compute: use case insensitive regexp for MatchOnly command
Created by: rvantonder
Stacked on https://github.com/sourcegraph/sourcegraph/pull/29998
Fixes https://github.com/sourcegraph/sourcegraph/issues/29932
Created by: rvantonder
Stacked on https://github.com/sourcegraph/sourcegraph/pull/29998
Fixes https://github.com/sourcegraph/sourcegraph/issues/29932