Sonatype snapshots failing again

They were fixed in https://github.com/google/auto/issues/1832 back in October, but they started failing again in late June. Here are [the last successful run](https://github.com/google/auto/actions/runs/15852754311/job/44690427381) and [the first failing run](https://github.com/google/auto/commit/87465e781f749fd0806eff35e25a1ca34e377fea). The first failure came after https://github.com/google/auto/pull/1933, but the failure at least naively seems unrelated to that:

`Error: Failed to execute goal org.apache.maven.plugins:maven-deploy-plugin:3.1.2:deploy (default-deploy) on project auto-common: Failed to deploy artifacts: Could not transfer artifact com.google.auto:auto-common:pom:HEAD-20250701.023018-657 from/to sonatype-nexus-snapshots (https://oss.sonatype.org/content/repositories/snapshots/): status code: 403, reason phrase: Forbidden (403) -> [Help 1]`

Granted, who knows, it could be that the new `maven-invoker-plugin` is trying to deploy itself when it shouldn't or something.