Revert "fiddle - Don't make warnings into errors."

This reverts commit b2031d4255.

Reason for revert: Breaks fiddle.

Original change's description:
> fiddle - Don't make warnings into errors.
> 
> Bug: skia:
> Change-Id: I01327003aa6a674dda9f8959fa69a386d0c017a8
> Reviewed-on: https://skia-review.googlesource.com/c/skia/+/183982
> Reviewed-by: Ravi Mistry <rmistry@google.com>
> Commit-Queue: Ravi Mistry <rmistry@google.com>
> Auto-Submit: Joe Gregorio <jcgregorio@google.com>

TBR=rmistry@google.com,jcgregorio@google.com

Change-Id: If85a7da4a523277208d197dc01e534aec2cc6d67
No-Presubmit: true
No-Tree-Checks: true
No-Try: true
Bug: skia:
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/269490
Reviewed-by: Joe Gregorio <jcgregorio@google.com>
Commit-Queue: Joe Gregorio <jcgregorio@google.com>

docker/skia-release/Dockerfile

@@ -24,7 +24,6 @@ extra_cflags = [  \n\
   "-I/tmp/swiftshader/include",  \n\
   "-DGR_EGL_TRY_GLES3_THEN_GLES2",  \n\
   "-g0",  \n\
-  "-Wno-error",  \n\
 ]  \n\
 extra_ldflags = [  \n\
   "-L/usr/local/lib",  \n\