fix: Migrate off TextPrinter's deprecated methods (#1452)

* fix: chore: Migrate off TextPrinter's deprecated methods

* 🦉 Updates from OwlBot post-processor

See https://github.com/googleapis/repo-automation-bots/blob/main/packages/owl-bot/README.md

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Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

google-cloud-datastore/src/main/java/com/google/cloud/datastore/Key.java

@@ -145,7 +145,7 @@ public Object getNameOrId() {
   /** Returns the key in an encoded form that can be used as part of a URL. */
   public String toUrlSafe() {
     try {
-      return URLEncoder.encode(TextFormat.printToString(toPb()), UTF_8.name());
+      return URLEncoder.encode(TextFormat.printer().printToString(toPb()), UTF_8.name());
     } catch (UnsupportedEncodingException e) {
       throw new IllegalStateException("Unexpected encoding exception", e);
     }