[ios-sdk] Fix label script

Summary: Need to pass -a to git tag because repo requires annotated tags.

Test Plan: Revert Plan:

Reviewers: jacl

Reviewed By: jacl

Differential Revision: https://phabricator.fb.com/D497679

scripts/label_version_number.sh

@@ -40,7 +40,7 @@ fi
 
 TAG_NAME=sdk-version-"$VERSION_STRING"
 
-git tag "$TAG_NAME" HEAD \
+git tag -a "$TAG_NAME" HEAD \
     || die 'Failed to tag HEAD. If this is a duplicate tag, please delete the old one first.'
 
 progress_message "Tagged HEAD as $TAG_NAME"