Bugfix for LOCAL_CERTIFICATE of AutogeneratedRuntimeResourceOverlay

LOCAL_CERTIFICATE of these modules are currently set to `PRESIGNED`,
since soong generates the build rules to sign the apk.

However, this is an incorrect interpretation of `PRESIGNED`. This
keyword means that the apk was signed with a release key, and not dev
keys. Since Soong signs the autogenerated rros with dev keys, drop
`PRESIGNED` from `LOCAL_CERTIFICATE` and replace it with the dev key
string.

Test: verified that `LOCAL_CERTIFICATE` of
`Settings__aosp_cf_x86_64_phone__auto_generated_rro_vendor` in the
autogenerated Android.mk is no longer PRESIGNED.

Bug: 375277835
Change-Id: I024f88f9ee887323e93df8338af5f8b089025b93