Update appveyor.yml to ignore x86 optimised failures
Update appveyor.yml to ignore x86 optimised failures

Several tests are currently failing due to what seems to be compiler bugs.

Ignore tests for now and revisit once MSVC 15.7 is released.
lewissbaker/cppcoro,lewissbaker/cppcoro,lewissbaker/cppcoro,lewissbaker/cppcoro