Fix punctuation in the string download_failed_we_cannot_download_the_file_without_storage_permission (#6473)

The double exclamation point is really unnecessary.

Author: amire80

app/src/main/res/values/strings.xml

@@ -538,7 +538,7 @@ Upload your first media by tapping on the add button.</string>
   <string name="welcome_do_upload_content_description">Examples of good images to upload to Commons</string>
   <string name="welcome_dont_upload_content_description">Examples of images not to upload</string>
   <string name="skip_image">Skip this image</string>
-  <string name="download_failed_we_cannot_download_the_file_without_storage_permission">Download Failed!!. We cannot download the file without external storage permission.</string>
+  <string name="download_failed_we_cannot_download_the_file_without_storage_permission">Download failed. We cannot download the file without external storage permission.</string>
 
   <string name="manage_exif_tags">Manage EXIF Tags</string>
   <string name="manage_exif_tags_summary">Select which EXIF tags to keep in uploads</string>