util: Remove unused `CombineGestures`

BUG=none
TEST=run the unit tests

Change-Id: Icc136fb509f5f72753f416a30a4280dc60d0be91
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/gestures/+/2293496
Tested-by: Harry Cutts <hcutts@chromium.org>
Auto-Submit: Harry Cutts <hcutts@chromium.org>
Reviewed-by: Sean O'Brien <seobrien@chromium.org>
Commit-Queue: Harry Cutts <hcutts@chromium.org>
4 files changed