[Cast Convergence] Remove is_chromecast from build_overrides/angle.gni.

is_chromecast is going to be removed from Chromium.  This flag is only
used in ANGLE when angle_has_build = true.

Upstream bug: https://crbug.com/1346787
Umbrella bug: https://crbug.com/1219802
Design doc (internal only): https://go/unified-cast-web-runtime

Bug: skia:13561
Change-Id: I7d739d99f67adc6a229f6dbf80e0e2b7a42829bf
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/562036
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
1 file changed