[PR #9455/d887930e backport][stable-10] normalize docs in callback plugins (#9467)

normalize docs in callback plugins (#9455)

* normalize docs in callback plugins

Normalize doc blocks for plugins

* Apply suggestions from code review

Co-authored-by: Felix Fontein <felix@fontein.de>

---------

Co-authored-by: Felix Fontein <felix@fontein.de>
(cherry picked from commit d887930e49)

Co-authored-by: Alexei Znamensky <103110+russoz@users.noreply.github.com>

plugins/callback/say.py

@@ -8,17 +8,17 @@
 from __future__ import (absolute_import, division, print_function)
 __metaclass__ = type
 
-DOCUMENTATION = '''
-    author: Unknown (!UNKNOWN)
-    name: say
-    type: notification
-    requirements:
-      - whitelisting in configuration
-      - the C(/usr/bin/say) command line program (standard on macOS) or C(espeak) command line program
-    short_description: notify using software speech synthesizer
-    description:
-      - This plugin will use the C(say) or C(espeak) program to "speak" about play events.
-'''
+DOCUMENTATION = r"""
+author: Unknown (!UNKNOWN)
+name: say
+type: notification
+requirements:
+  - whitelisting in configuration
+  - the C(/usr/bin/say) command line program (standard on macOS) or C(espeak) command line program
+short_description: notify using software speech synthesizer
+description:
+  - This plugin will use the C(say) or C(espeak) program to "speak" about play events.
+"""
 
 import platform
 import subprocess