Add notice of requesting source code in media and media swcodec

Flag: EXEMPT license change for b/418865751
Bug: 418865751
Test: presubmits
Test: lunch husky-trunk_staging-eng && m, an extra line is added at the top of NOTICE.html file in NOTICE.html.gz
Change-Id: Id9c729d8d6d1b00414ffa5364929315da7b0d55a