fix(changelog): fix the broken link to commitlintrc.js

The link to commitlintrc.js file in the v2.7 changelog
is updated.

Change-Id: I24ee736180d8df72b2d831e110a9a3a80a6d9862
Signed-off-by: Jayanth Dodderi Chidanand <jayanthdodderi.chidanand@arm.com>