gradle: upgrade AndroidX dependencies

Signed-off-by: Harsh Shandilya <me@msfjarvis.dev>

ui/build.gradle

@@ -12,7 +12,7 @@ group groupName
 final def keystorePropertiesFile = rootProject.file("keystore.properties")
 
 android {
-    compileSdkVersion 30
+    compileSdkVersion 31
     buildFeatures {
         buildConfig = true
         dataBinding = true

ui/src/main/java/com/wireguard/android/activity/LogViewerActivity.kt

@@ -126,9 +126,9 @@ class LogViewerActivity : AppCompatActivity() {
         }
     }
 
-    override fun onCreateOptionsMenu(menu: Menu?): Boolean {
+    override fun onCreateOptionsMenu(menu: Menu): Boolean {
         menuInflater.inflate(R.menu.log_viewer, menu)
-        saveButton = menu?.findItem(R.id.save_log)
+        saveButton = menu.findItem(R.id.save_log)
         return true
     }