[PR #5918/393f2d61 backport][stable-6] Fix PLATFORM attributes docs fragment (#5919)

Fix PLATFORM attributes docs fragment (#5918)

Fix PLATFORM attributes docs fragment.

(cherry picked from commit 393f2d6153)

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

plugins/doc_fragments/attributes.py

@@ -21,6 +21,8 @@ attributes:
 '''
 
     PLATFORM = r'''
+options: {}
+attributes:
     platform:
       description: Target OS/families that can be operated against.
       support: N/A