Fix issue with not resetting valueLength

dotnet#78881 was just merged with a small bug, in that valueLength wasn't reset before it was used a second time. If the typeName is > 64 chars, then this would have thrown a different exception than it should have down a couple lines.

Author: ToddGrun

src/LanguageServer/Protocol/Protocol/Internal/Converters/ImageElementConverter.cs

@@ -48,6 +48,8 @@ public override ImageElement Read(ref Utf8JsonReader reader, Type typeToConvert,
                             automationName = reader.GetString();
                             break;
                         case ObjectContentConverter.TypeProperty:
+                            valueLength = reader.HasValueSequence ? reader.ValueSequence.Length : reader.ValueSpan.Length;
+
                             var typePropertyLength = valueLength <= scratchChars.Length ? reader.CopyString(scratchChars) : -1;
                             var typeProperty = typePropertyLength >= 0 ? scratchChars[..typePropertyLength] : reader.GetString().AsSpan();
 

src/LanguageServer/Protocol/Protocol/Internal/Converters/ImageIdConverter.cs

@@ -49,6 +49,8 @@ public override ImageId Read(ref Utf8JsonReader reader, Type objectType, JsonSer
                             id = reader.GetInt32();
                             break;
                         case ObjectContentConverter.TypeProperty:
+                            valueLength = reader.HasValueSequence ? reader.ValueSequence.Length : reader.ValueSpan.Length;
+
                             var typePropertyLength = valueLength <= scratchChars.Length ? reader.CopyString(scratchChars) : -1;
                             var typeProperty = typePropertyLength >= 0 ? scratchChars[..typePropertyLength] : reader.GetString().AsSpan();