re-enable rule to check for sentence case in headings

Signed-off-by: Alexa Kreizinger <[email protected]>

Author: alexakreizinger

.vale.ini

@@ -11,7 +11,7 @@ BasedOnStyles = FluentBit
 FluentBit.Terms = YES
 FluentBit.Titles = YES
 FluentBit.FutureTense = NO
-FluentBit.Headings = NO
+FluentBit.Headings = YES
 FluentBit.Passive = NO
 FluentBit.Subjunctive = NO
 FluentBit.Colons = NO