Give LongScreenshotActivity a "Capture more" label

It's read out by accessibility. Otherwise it just says "system UI".

Test: Enable talkback, listen when activity is invoked.
Bug: 208713927
Change-Id: I0d1714fc6492221cd803affaea1de7833f560749
diff --git a/packages/SystemUI/AndroidManifest.xml b/packages/SystemUI/AndroidManifest.xml
index e24b2d6..18385c2 100644
--- a/packages/SystemUI/AndroidManifest.xml
+++ b/packages/SystemUI/AndroidManifest.xml
@@ -380,6 +380,7 @@
                   android:theme="@style/LongScreenshotActivity"
                   android:process=":screenshot"
                   android:exported="false"
+                  android:label="@string/screenshot_scroll_label"
                   android:finishOnTaskLaunch="true" />
 
         <service android:name=".screenrecord.RecordingService" />