Rename source_prereqs to inputs in the GN Build file.
Rename source_prereqs to inputs in the GN Build file.

See more information in the gn-dev mailing list:
https://groups.google.com/a/chromium.org/d/msg/gn-dev/j-P5hlvZ13M/4CSw2WworlkJ

Also in
https://chromium.googlesource.com/chromium/src/+/61a6fca4bca5438bf4338184c29fded55e5f240e

BUG=374271
R=machenbach@chromium.org
LOG=N

Review URL: https://codereview.chromium.org/917243002

Cr-Commit-Position: 972c6d2dc6dd5efdad1377c0d224e03eb8f276f7@{#26658}

UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh,UniversalFuture/moosh