project.config: grant submit access to the 1.23 release branch

For go.dev/issue/67586.

Change-Id: If1ece98d348296cadb65dc4e38c94bba8ac1c227
Reviewed-on: https://go-review.googlesource.com/c/All-Projects/+/600136
Reviewed-by: Cherry Mui <cherryyz@google.com>