Remove explicit configuration of https://central.sonatype.com/repository/maven-snapshots.

[copybara-service]

Remove explicit configuration of https://central.sonatype.com/repository/maven-snapshots.

@Marcono1234 notes in a GSON PR that this appears to be the default. So let's not re-specify the default. (Compare cl/799337152.)

If this CL goes well, I'll mail a similar CL (cl/805841232) for our other projects.

RELNOTES=n/a

[cpovirk]

OK, this led to an error:

Error:  Failed to execute goal org.apache.maven.plugins:maven-deploy-plugin:3.1.2:deploy (default-deploy) on project truth-parent: Deployment failed: repository element was not specified in the POM inside distributionManagement element or in -DaltDeploymentRepository=id::url parameter -> [Help 1]

Maybe we need to explicitly disable the maven-deploy-plugin? central-publishing-maven-plugin already somewhat disables it, but maybe we need to disable it harder so that it doesn't even try to read its properties?

[cpovirk]

I can disable maven-deploy-plugin with <skip>true</skip> in configuration or with...

<execution>
  <id>default-deploy</id>
  <phase>none</phase>
</execution>

...in executions. But then... nothing gets deployed (for snapshots, anyway, which is what I've been testing). So I guess that snapshot publication still uses maven-deploy-plugin?

Oh: Maybe that's because I have central-publishing-maven-plugin configured only in our sonatype-oss-release profile, which we don't enable for snapshots. I probably need to enable it for all builds (though it will do nothing without deploy or a similar command).

OK, yes, that appears to work.

[cpovirk]

(The saga here is ongoing and has been chronicled in google/auto#1965, which the the wrong place to chronicle it. I expect that snapshotswill be working again, now through central-publishing-maven-plugin, after #1597. But then I have expected snapshots to be working for a while now... :))