lint: Re-enable imperative-mood checking.

This was mistakenly disabled in e1f943913a.  Re-enable it.

.gitlint

@@ -1,5 +1,5 @@
 [general]
-ignore=title-trailing-punctuation, body-min-length, body-is-missing, title-imperative-mood
+ignore=title-trailing-punctuation, body-min-length, body-is-missing
 
 extra-path=tools/lib/gitlint-rules.py
 

tools/lib/gitlint-rules.py

@@ -305,7 +305,9 @@ class ImperativeMood(LineRule):
             violation = RuleViolation(
                 self.id,
                 self.error_msg.format(
-                    word=first_word, imperative=imperative, title=commit.message.title,
+                    word=first_word,
+                    imperative=imperative,
+                    title=commit.message.title,
                 ),
             )