updating gradle/README.md to mention development/update-verification-metadata.sh
updating gradle/README.md to mention development/update-verification-metadata.sh

for updating dependency verification information

Bug: 223642687
Change-Id: I4382248c5b3f1fbee7d8104974ab3d92e2652f56

AndroidX/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx,AndroidX/androidx,AndroidX/androidx,androidx/androidx,androidx/androidx,androidx/androidx,AndroidX/androidx,androidx/androidx