chore: Apply whitespace fixes from hooks

- Remove trailing whitespace
- Correct single newline at end of files (skip for json)
- Update to formatting in a few places due to black

help/en/preferences.rst

@@ -67,11 +67,11 @@ filename if the filename already exists in the destination.
 The format of the command is the same as what you would write in the command line, except that there
 are 2 placeholders: **%d** and **%r**. These placeholders will be replaced by the path of the
 selected dupe (%d) and the path of the selected dupe's reference file (%r).
-  
+
 If the path to your executable contains space characters, you should enclose it in "" quotes. You
 should also enclose placeholders in quotes because it's very possible that paths to dupes and refs
 will contain spaces. Here's an example custom command::
-  
+
     "C:\Program Files\SuperDiffProg\SuperDiffProg.exe" "%d" "%r"
 
 .. _inode: http://en.wikipedia.org/wiki/Inode