omit the unused catch binding

thanks to https://github.com/tc39/proposal-optional-catch-binding

[BREAKING] drop support for Node.js < 10

index.js

@@ -8,7 +8,7 @@ module.exports = function sassPackageImporter(path, prev, done) {
 
 	try {
 		resolvedPath = require.resolve(path);
-	} catch (err) {
+	} catch {
 		done({file: path});
 		return;
 	}