Update TestGrid link in README.md (#310)

Remove stale TestGrid link from README.md

Author: TristonianJones

README.md

@@ -60,10 +60,6 @@ For more detail, see:
 *   [Introduction](doc/intro.md)
 *   [Language Definition](doc/langdef.md)
 
-A dashboard that shows results of conformance tests on current CEL
-implementations can be found
-[here](https://k8s-testgrid.appspot.com/google-cel).
-
 Released under the [Apache License](LICENSE).
 
 Disclaimer: This is not an official Google product.