Update README.md

packages/flutter/README.md

@@ -58,7 +58,7 @@ of the Android operating system.
   - Mac: `brew install android-platform-tools`
   - Linux: `sudo apt-get install android-tools-adb`
     - If the version of `adb` provided by your Linux distribution is too old,
-      you might need to (install the Android SDK manually)[https://developer.android.com/sdk/installing/index.html?pkg=tools].
+      you might need to [install the Android SDK manually](https://developer.android.com/sdk/installing/index.html?pkg=tools]).
 
  - Enable developer mode on your device by visiting `Settings > About phone`
    and tapping the `Build number` field five times.