validate: yamllint: set locale in config file

Signed-off-by: Sebastiaan van Stijn <github@gone.nl>

hack/validate/swagger

@@ -8,7 +8,7 @@ files=($(validate_diff --diff-filter=ACMR --name-only -- 'api/swagger.yaml' || t
 unset IFS
 
 if [ -n "${TEST_FORCE_VALIDATE:-}" ] || [ ${#files[@]} -gt 0 ]; then
-	LANG=C.UTF-8 yamllint -f parsable -c "${SCRIPTDIR}"/yamllint.yaml api/swagger.yaml
+	yamllint -f parsable -c "${SCRIPTDIR}"/yamllint.yaml api/swagger.yaml
 	if out=$(swagger validate api/swagger.yaml); then
 		echo "Congratulations!  ${out}"
 	else

hack/validate/yamllint.yaml

@@ -1,4 +1,5 @@
 extends: default
+locale: C.UTF-8
 rules:
   document-start: disable
   line-length: disable