deprecation link in java-spanner repo's README was not added correctly

[glasser]

A few weeks ago, the repo https://github.com/googleapis/java-spanner was archived.

@chingor13 made the PR googleapis/java-spanner#4397 (reviewed by @lqiu96) which was supposed to add a message to that repo's README linking to this one.

However, @cloud-java-bot added a second commit to the PR before it was merged, which reverted that change. So the final commit in that repo is an empty commit, and you can only find the deprecation notice and link to this PR by viewing the PR itself.

[lqiu96]

Thanks for reporting this! We will fix and add the redirection notice.