doc: Fix URLs

Don't use Markdown markup as it looks odd in the generated page.

doc/feedback-themes.rst

@@ -16,8 +16,8 @@ In order to reflect device specifics and user overrides the feedback
 be configured and overridden by so called themes. Feedback themes use a JSON
 format that can be validated with ``fbd-theme-validate``.
 
-For details on how to create or modify feedback themes see [feedbackd's documentation](
-https://source.puri.sm/Librem5/feedbackd#feedback-theme).
+For details on how to create or modify feedback themes see
+``feedbackd's documentation`` at https://source.puri.sm/Librem5/feedbackd#feedback-theme
 
 Feedback types
 --------------
@@ -33,7 +33,7 @@ Sound feedback
 ~~~~~~~~~~~~~~
 
 Sound feedbacks specify an event name from a XDG sound theme. Sound themes
-are described in the [Sound theme spec](https://freedesktop.org/wiki/Specifications/sound-theme-spec/).
+are described in the ``Sound theme spec`` at https://freedesktop.org/wiki/Specifications/sound-theme-spec/
 
 VibraRumble feedback
 ~~~~~~~~~~~~~~~~~~~~