Update index.md (#1954)
Update index.md (#1954)

* Update index.md

Removed unnecessary punctuation marks and words.
Moved text to a Notes section since it looked like it should be called out that way.

* Update guides/user/pipeline/triggers/github/index.md

Co-authored-by: Dave Dorbin <3a983b921291999521a653180c5b82ccd2c36700@google.com>

Co-authored-by: Dave Dorbin <3a983b921291999521a653180c5b82ccd2c36700@google.com>
Co-authored-by: brian-armory <351c5a34dfc775063ffb19a2eb79e47e316c1f67@users.noreply.github.com>
spinnaker/spinnaker.github.io,spinnaker/spinnaker.github.io,spinnaker/spinnaker.github.io