fixup! lint(yaml): Only use true and false boolean values

Don't change yamllint policy as other components still not compliant.

Signed-off-by: 林博仁(Buo-ren Lin) <buo.ren.lin@gmail.com>

.yamllint

@@ -133,5 +133,5 @@ rules:
   # Use this rule to forbid non-explictly typed truthy values other than `true` and `false`, for example `YES`, `False` and `off`.
   # https://yamllint.readthedocs.io/en/stable/rules.html#module-yamllint.rules.truthy
   truthy:
-    allowed-values: ['true', 'false']
+    level: warning
 ...