Fix wrong casing of file endings from BMP to bmp

tests/ImageSharp.Tests/TestImages.cs

@@ -377,14 +377,14 @@ public static class TestImages
         public const string Os2v2Short = "Bmp/pal8os2v2-16.bmp";
         public const string Os2v2 = "Bmp/pal8os2v2.bmp";
         public const string Os2BitmapArray = "Bmp/ba-bm.bmp";
-        public const string Os2BitmapArray9s = "Bmp/9S.BMP";
-        public const string Os2BitmapArrayDiamond = "Bmp/DIAMOND.BMP";
-        public const string Os2BitmapArrayMarble = "Bmp/GMARBLE.BMP";
-        public const string Os2BitmapArraySkater = "Bmp/SKATER.BMP";
-        public const string Os2BitmapArraySpade = "Bmp/SPADE.BMP";
-        public const string Os2BitmapArraySunflower = "Bmp/SUNFLOW.BMP";
-        public const string Os2BitmapArrayWarpd = "Bmp/WARPD.BMP";
-        public const string Os2BitmapArrayPines = "Bmp/PINES.BMP";
+        public const string Os2BitmapArray9s = "Bmp/9S.bmp";
+        public const string Os2BitmapArrayDiamond = "Bmp/DIAMOND.bmp";
+        public const string Os2BitmapArrayMarble = "Bmp/GMARBLE.bmp";
+        public const string Os2BitmapArraySkater = "Bmp/SKATER.bmp";
+        public const string Os2BitmapArraySpade = "Bmp/SPADE.bmp";
+        public const string Os2BitmapArraySunflower = "Bmp/SUNFLOW.bmp";
+        public const string Os2BitmapArrayWarpd = "Bmp/WARPD.bmp";
+        public const string Os2BitmapArrayPines = "Bmp/PINES.bmp";
         public const string LessThanFullSizedPalette = "Bmp/pal8os2sp.bmp";
         public const string Pal8Offset = "Bmp/pal8offs.bmp";
         public const string OversizedPalette = "Bmp/pal8oversizepal.bmp";