Update language file: shorten "Flip horizontally" labels in `en.json`.

src/PicView.Core/Config/Languages/en.json

@@ -140,8 +140,8 @@
   "FlashEnergy": "Flash energy",
   "FlashFired": "Flash fired",
   "FlashMode": "Flash mode",
-  "Flip": "Flip horizontally",
-  "Flipped": "Flipped horizontally",
+  "Flip": "Flip",
+  "Flipped": "Flipped",
   "Fluorescent": "Fluorescent",
   "FocalLength": "Focal length",
   "FocalLength35mm": "Focal length 35mm",