docs: cleanup header levels in backend docs (#5698)

docs/content/b2.md

@@ -10,6 +10,8 @@ B2 is [Backblaze's cloud storage system](https://www.backblaze.com/b2/).
 Paths are specified as `remote:bucket` (or `remote:` for the `lsd`
 command.)  You may put subdirectories in too, e.g. `remote:bucket/path/to/dir`.
 
+## Configuration
+
 Here is an example of making a b2 configuration.  First run
 
     rclone config
@@ -71,7 +73,7 @@ excess files in the bucket.
 
     rclone sync -i /home/local/directory remote:bucket
 
-### Application Keys ###
+### Application Keys
 
 B2 supports multiple [Application Keys for different access permission
 to B2 Buckets](https://www.backblaze.com/b2/docs/application_keys.html).
@@ -87,13 +89,13 @@ Note that you must put the _applicationKeyId_ as the `account` – you
 can't use the master Account ID.  If you try then B2 will return 401
 errors.
 
-### --fast-list ###
+### --fast-list
 
 This remote supports `--fast-list` which allows you to use fewer
 transactions in exchange for more memory. See the [rclone
 docs](/docs/#fast-list) for more details.
 
-### Modified time ###
+### Modified time
 
 The modified time is stored as metadata on the object as
 `X-Bz-Info-src_last_modified_millis` as milliseconds since 1970-01-01
@@ -104,7 +106,7 @@ Modified times are used in syncing and are fully supported. Note that
 if a modification time needs to be updated on an object then it will
 create a new version of the object.
 
-#### Restricted filename characters
+### Restricted filename characters
 
 In addition to the [default restricted characters set](/overview/#restricted-characters)
 the following characters are also replaced:
@@ -122,7 +124,7 @@ re-transfer files. If you want rclone not to replace \ then see the
 `--b2-encoding` flag below and remove the `BackSlash` from the
 string. This can be set in the config.
 
-### SHA1 checksums ###
+### SHA1 checksums
 
 The SHA1 checksums of the files are checked on upload and download and
 will be used in the syncing process.
@@ -144,7 +146,7 @@ large files without SHA1 checksums.  This may be fixed in the future
 Files sizes below `--b2-upload-cutoff` will always have an SHA1
 regardless of the source.
 
-### Transfers ###
+### Transfers
 
 Backblaze recommends that you do lots of transfers simultaneously for
 maximum speed.  In tests from my SSD equipped laptop the optimum
@@ -159,7 +161,7 @@ a 96 MiB RAM buffer by default.  There can be at most `--transfers` of
 these in use at any moment, so this sets the upper limit on the memory
 used.
 
-### Versions ###
+### Versions
 
 When rclone uploads a new version of a file it creates a [new version
 of it](https://www.backblaze.com/b2/docs/file_versions.html).
@@ -223,7 +225,7 @@ $ rclone -q --b2-versions ls b2:cleanup-test
         9 one.txt
 ```
 
-### Data usage ###
+### Data usage
 
 It is useful to know how many requests are sent to the server in different scenarios.
 
@@ -261,7 +263,7 @@ start and finish the upload) and another 2 requests for each chunk:
 /b2api/v1/b2_finish_large_file
 ```
 
-#### Versions ####
+#### Versions
 
 Versions can be viewed with the `--b2-versions` flag. When it is set
 rclone will show and act on older versions of files.  For example
@@ -290,7 +292,7 @@ server to the nearest millisecond appended to them.
 Note that when using `--b2-versions` no file write operations are
 permitted, so you can't upload files or delete them.
 
-### B2 and rclone link ###
+### B2 and rclone link
 
 Rclone supports generating file share links for private B2 buckets.
 They can either be for a file for example:
@@ -509,7 +511,8 @@ See: the [encoding section in the overview](/overview/#encoding) for more info.
 - Default:     Slash,BackSlash,Del,Ctl,InvalidUtf8,Dot
 
 {{< rem autogenerated options stop >}}
-### Limitations
+
+## Limitations
 
 `rclone about` is not supported by the B2 backend. Backends without
 this capability cannot determine free space for an rclone mount or