Disable wxWebView in ASAN CI build

Running wxWebView tests with ASAN results in "ASan runtime does not come
first in initial library list" warnings and doesn't work currently, so
disable wxWebView in this build for now to have a chance of passing the
tests.

It would be better to actually fix this, of course, but this will have
to wait until later.

.github/workflows/ci.yml

@@ -51,7 +51,7 @@ jobs:
             skip_samples: true
           - name: Ubuntu 20.04 wxGTK with ASAN
             runner: ubuntu-20.04
-            configure_flags: --disable-compat30 --disable-sys-libs --with-libcurl
+            configure_flags: --disable-compat30 --disable-sys-libs --with-libcurl --disable-webview
             skip_samples: true
             use_asan: true
             use_xvfb: true