http2_request: Disable build in CI

- Tracked by IDF-4916

examples/protocols/http2_request/README.md

@@ -1,3 +1,6 @@
+| Supported Targets | Linux |
+| ----------------- | ----- |
+
 # HTTP/2 Request Example
 
 Establish an HTTP/2 connection with https://http2.github.io