Revert "meta: Lower Dart SDK requirement"

This reverts commit fafc4f2320.

.gitlint

@@ -5,6 +5,6 @@ line-length=72
 [title-trailing-punctuation]
 [title-hard-tab]
 [title-match-regex]
-regex=^(feat|fix|test|release|chore|security|docs|refactor|meta):.*$
+regex=^(feat|fix|test|release|chore|security|docs|refactor):.*$
 [body-trailing-whitespace]
 [body-first-line-empty]