[image_picker]: Bump gradle

Bumps gradle from 3.3.0 to 7.1.3.

---
updated-dependencies:
- dependency-name: com.android.tools.build:gradle
  dependency-type: direct:production
  update-type: version-update:semver-major
...

Signed-off-by: dependabot[bot] <support@github.com>

Author: dependabot[bot]

packages/image_picker/image_picker_android/android/build.gradle

@@ -8,7 +8,7 @@ buildscript {
     }
 
     dependencies {
-        classpath 'com.android.tools.build:gradle:3.3.0'
+        classpath 'com.android.tools.build:gradle:7.1.3'
     }
 }