rewrite-gradle-plugin snapshots to ossrh

[aegershman]

See: openrewrite/rewrite-maven-plugin#265

Publish rewrite-gradle-plugin snapshots to ossrh snapshots.
This will make it more convenient to consume and validate changes prior to release.

Be aware that to resolve plugins from anywhere other than the gradle plugin portal, you need a snippet like this in the settings.gradle.kts

pluginManagement {
    repositories {
        // ...
        maven {
            url = uri("https://oss.sonatype.org/content/repositories/snapshots/")
        }
        // ...
        // you'll likely also need this if you don't have a pluginManagement section already:
        gradlePluginPortal()
        // ...
    }
}

Gradle plugin portal doesn't accept snapshots, but that's alright. We'll push snapshots to OSSRH, and can keep publishing releases just to gradlePluginPortal.