Allow SkIcoCodec to fail due to conversion

src/codec/SkCodec_libico.cpp

Index: src/codec/SkCodec_libico.cpp
diff --git a/src/codec/SkCodec_libico.cpp b/src/codec/SkCodec_libico.cpp
index 8b38148adff6e72872c4e642a44eba1d4c4ab5a7..62562a19d5240acbbc8201c263933450723621a8 100644
--- a/src/codec/SkCodec_libico.cpp
+++ b/src/codec/SkCodec_libico.cpp
@@ -293,9 +293,6 @@ SkCodec::Result SkIcoCodec::onGetPixels(const SkImageInfo& dstInfo,
         }
     }
 
-    // This should never be reached, since onDimensionsSupported should have rejected the
-    // dimensions sooner.
-    SkASSERT(false);
     SkCodecPrintf("Error: No matching candidate image in ico.\n");
     return result;
 }