libweave: post libchrome r860220 uprev clean-up

Remove BASE_VER macro guards.

BUG=chromium:1179608
TEST=FEATURES=test emerge-hatch libweave

Change-Id: Ia75cb9800e76f842963398e2c0e52f6a787adc04
Reviewed-on: https://chromium-review.googlesource.com/c/weave/libweave/+/2939121
Tested-by: Grace Cham <hscham@chromium.org>
Reviewed-by: Qijiang Fan <fqj@google.com>
Commit-Queue: Grace Cham <hscham@chromium.org>