Update html notice to include a notice of requesting source code

Bug: 418865751
Test: lunch husky-trunk_staging-eng && m com.google.android.adbd, an
extra line is added at the top of NOTICE.html file in NOTICE.html.gz
Test: presubmits

Change-Id: I3a90ef57c36d67a879130d57cd66e735a5c1e5a0