docs: drop the test count from the README

A number that has to be updated on every commit that adds a test, and
means nothing to a reader either way. What matters is that the suite
needs no Gateway and no Hookdeck account, which is what it now says.

Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Author: garethx

README.md

@@ -146,7 +146,7 @@ The README covers the common path. Everything else lives in [`docs/`](docs/):
 
 ```bash
 openclaw plugins install --link ./hookdeck-openclaw
-npm test   # 613 tests, no Hookdeck account required
+npm test   # no Gateway or Hookdeck account required
 ```
 
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