Revert "fix: correct reading of sync-labels input. (#480)" (#564)

This reverts commit 751921c443.

src/labeler.ts

@@ -15,7 +15,7 @@ export async function run() {
   try {
     const token = core.getInput('repo-token');
     const configPath = core.getInput('configuration-path', {required: true});
-    const syncLabels = core.getBooleanInput('sync-labels');
+    const syncLabels = !!core.getInput('sync-labels', {required: false});
 
     const prNumber = getPrNumber();
     if (!prNumber) {