fix typo in SkJpegCodec.cpp

The missing break rejects grayscale profiles for grayscale images.

Change-Id: I16ad8e7b581f009257a47c4e0f45f7b3c0008487
Reviewed-on: https://skia-review.googlesource.com/66140
Reviewed-by: Mike Klein <mtklein@chromium.org>
Commit-Queue: Mike Klein <mtklein@chromium.org>

src/codec/SkJpegCodec.cpp

@@ -243,6 +243,7 @@ SkCodec::Result SkJpegCodec::ReadHeader(SkStream* stream, SkCodec** codecOut,
                     {
                         colorSpace = nullptr;
                     }
+                    break;
                 default:
                     if (colorSpace->type() != SkColorSpace::kRGB_Type) {
                         colorSpace = nullptr;