Change EXIF to Exif

Per https://en.wikipedia.org/wiki/Exchangeable_image_file_format. Spotted
by Shirayuki and documented on
https://translatewiki.net/wiki/Thread:Support/About_MediaWiki:Sesp-property-exif-data/en

Change-Id: I84d9ef123e8581bb34cad5baec17083f442517fe