tree: Fix various typos and outdated terminology

This was mostly machine generated with the following command:
```
codespell \
    --builtin clear,rare,usage \
    --skip './po/*' --skip './.git/*' --skip './NEWS*' \
    --write-changes .
```
using the latest git version of `codespell` as per [these
instructions](https://github.com/codespell-project/codespell#user-content-updating).

Then I manually checked each change using `git add -p`, made a few
manual fixups and dropped a load of incorrect changes.

There are still some outdated or loaded terms used in GLib, mostly to do
with git branch terminology. They will need to be changed later as part
of a wider migration of git terminology.

If I’ve missed anything, please file an issue!

Signed-off-by: Philip Withnall <withnall@endlessm.com>

gio/gdrive.c

@@ -45,7 +45,7 @@
  *
  * If the #GDrive reports that media isn't automatically detected, one
  * can poll for media; typically one should not do this periodically
- * as a poll for media operation is potententially expensive and may
+ * as a poll for media operation is potentially expensive and may
  * spin up the drive creating noise.
  *
  * #GDrive supports starting and stopping drives with authentication
@@ -249,9 +249,9 @@ g_drive_get_volumes (GDrive *drive)
  * g_drive_is_media_check_automatic:
  * @drive: a #GDrive.
  * 
- * Checks if @drive is capabable of automatically detecting media changes.
+ * Checks if @drive is capable of automatically detecting media changes.
  * 
- * Returns: %TRUE if the @drive is capabable of automatically detecting 
+ * Returns: %TRUE if the @drive is capable of automatically detecting
  *     media changes, %FALSE otherwise.
  **/
 gboolean