Add notice of requesting source code in statsd

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
(cherry picked from https://googleplex-android-review.googlesource.com/q/commit:ade2df3bae17981af4acc9dc2004ff23dbea428f)
Merged-In: Ibb69e3a8e2c832aebdc9cddc8380994832749695
Change-Id: Ibb69e3a8e2c832aebdc9cddc8380994832749695