router: Remove the HeaderMatcher value and regex fields. (#3796)
router: Remove the HeaderMatcher value and regex fields. (#3796)

Signed-off-by: Kavya Kotacherry <kavyako@microsoft.com>

Mirrored from https://github.com/envoyproxy/envoy @ 5e1eb028c0240b5cf0a2f86cfacb105d2c75c371

lyft/envoy-api,lyft/envoy-api,lyft/envoy-api