[AW] Use WebView's LicenseContentProvider in Monochrome

This deletes Monochrome's LicenseContentProvider and makes it use
WebView's implementation as SystemWebView and Trichrome do.

Test: Start monochrome's LicenseActivity, then start monochrome
Bug: 934152
Change-Id: I8db38a219c932726659af08593aad6a9b7c178ba
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1860402
Reviewed-by: Andrew Grieve <agrieve@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Commit-Queue: Robbie McElrath <rmcelrath@chromium.org>
Cr-Commit-Position: refs/heads/master@{#707651}

• BUILD.gn[diff]
• android_webview/BUILD.gn[diff]
• android_webview/apk/BUILD.gn[diff]
• android_webview/apk/java/src/com/android/webview/chromium/LicenseContentProvider.java[diff]
• android_webview/system_webview_apk_tmpl.gni[diff]
• chrome/android/chrome_public_apk_tmpl.gni[diff]
• chrome/android/monochrome/BUILD.gn[diff]
• chrome/android/monochrome/java/DEPS[Deleted - diff]
• chrome/android/monochrome/java/src/com/android/webview/chromium/LicenseContentProvider.java[Deleted - diff]