Enable the unicorn/prefer-optional-catch-binding ESLint plugin rule

According to MDN this format is available in all browsers/environments that we currently support, see https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Statements/try...catch#browser_compatibility

Please also see https://github.com/sindresorhus/eslint-plugin-unicorn/blob/main/docs/rules/prefer-optional-catch-binding.md

src/scripting_api/aform.js

@@ -144,7 +144,7 @@ class AForm {
     let date = null;
     try {
       date = this._util.scand(cFormat, cDate);
-    } catch (error) {}
+    } catch {}
     if (!date) {
       date = Date.parse(cDate);
       if (isNaN(date)) {