docs: de-hardcode the initial-publish section in RELEASING.md

[OmarAlJarrah]

Summary

• RELEASING.md's "Publishing the initial 0.1.0-alpha.1" section still assumed .release-please-manifest.json and gradle.properties read 0.1.0-alpha.1 and that the next automated release would be alpha.2; both files are now at 0.1.0-alpha.4, so the runbook pointed at a stale version and a false "next release" claim.
• Reworded the section to describe the actual condition that requires a manual publish -- release-please's publish job builds off an existing GitHub Release, so a version with no prior tag (the very first alpha, or the start of a future series) has to be published by hand once -- instead of naming a specific version number.
• This keeps the runbook accurate as releases keep shipping and lets it apply again if a future series ever needs the same manual bootstrap, rather than needing another edit every time the version moves.

Test plan

• Doc-only change (no logic touched); proofread the diff for accuracy against the current .release-please-manifest.json (0.1.0-alpha.4) and gradle.properties (version=0.1.0-alpha.4).
• No Gradle build required per repo policy for doc-only changes.

Closes #94

[OmarAlJarrah]

Superseded by #157, which switches the project to a stable 0.1.0 release line. This PR's de-hardcoded, generic "bootstrap a version with no prior tag" runbook is incorporated into the RELEASING.md rework there, alongside the broader alpha-to-0.x cadence changes the version switch requires. Closing in favor of #157; #94 is closed there.