docs: fix heading levels so sections appear in the table of contents

The "Import/Export of google documents" section in drive.md and the
"--b2-versions" examples section in b2.md were both at H4 instead of H3,
which excluded them from the ToC even though they are top-level topics
in their respective sections.

docs/content/b2.md

@@ -314,7 +314,7 @@ start and finish the upload) and another 2 requests for each chunk:
 /b2api/v1/b2_finish_large_file
 ```
 
-#### Versions
+### Viewing versions with --b2-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

docs/content/drive.md

@@ -496,7 +496,7 @@ Drive, the size of all files in the Trash and the space used by other
 Google services such as Gmail. This command does not take any path
 arguments.
 
-#### Import/Export of google documents
+### Import/Export of google documents
 
 Google documents can be exported from and uploaded to Google Drive.