Fix inconsistent capitalization in IVideoWriter.ToString()

Author: nattthebear

BizHawk.MultiClient/AVOut/AviWriter.cs

@@ -789,7 +789,7 @@ public unsafe void AddFrame(IVideoProvider source)
 
 		public override string ToString()
 		{
-			return "avi writer";
+			return "AVI writer";
 		}
 
 		public string WriterDescription()

BizHawk.MultiClient/AVOut/FFmpegWriter.cs

@@ -263,7 +263,7 @@ public void SetAudioParameters(int sampleRate, int channels, int bits)
 
 		public override string ToString()
 		{
-			return "ffmpeg writer";
+			return "FFmpeg writer";
 		}
 
 		public string WriterDescription()

BizHawk.MultiClient/AVOut/GifWriter.cs

@@ -234,7 +234,7 @@ public void Dispose()
 
 		public override string ToString()
 		{
-			return "gif writer";
+			return "GIF writer";
 		}
 	}
 }

BizHawk.MultiClient/AVOut/NutWriter.cs

@@ -128,7 +128,7 @@ public void Dispose()
 
 		public override string ToString()
 		{
-			return ".nut writer";
+			return "NUT writer";
 		}
 
 		public string WriterDescription()

BizHawk.MultiClient/AVOut/WavWriter.cs

@@ -271,7 +271,7 @@ public void AddSamples(short[] samples)
 
 		public override string ToString()
 		{
-			return ".wav writer";
+			return "WAV writer";
 		}
 
 		public string WriterDescription()