Removed getSupportActionBar command

The getSupportActionBar method caused a null pointer exception in deviced running Android SDK >21 but there is actually no need for it since the theme doesn't have an Action Bar.

Author: ftsalamp

app/src/main/java/fr/free/nrw/commons/auth/SignupActivity.java

@@ -20,8 +20,6 @@ protected void onCreate(Bundle savedInstanceState) {
         super.onCreate(savedInstanceState);
         Timber.d("Signup Activity started");
 
-        getSupportActionBar().hide();
-
         webView = new WebView(this);
         setContentView(webView);