docs: update websocket.rst (#6546)
docs: update websocket.rst (#6546)

Link to RFC 8441 rather than the earlier working group draft.
Fixes #6528

Signed-off-by: James Synge <e7be15b37e5ccbb74d0b5c250ed243abe0e2913a@google.com>

lyft/envoy,envoyproxy/envoy-wasm,istio/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy,envoyproxy/envoy,eklitzke/envoy,envoyproxy/envoy-wasm,lizan/envoy,jrajahalme/envoy,envoyproxy/envoy-wasm,jrajahalme/envoy,envoyproxy/envoy,istio/envoy,lyft/envoy,dnoe/envoy,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,dnoe/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,dnoe/envoy,istio/envoy,istio/envoy,envoyproxy/envoy,jrajahalme/envoy,lizan/envoy,lyft/envoy,eklitzke/envoy,envoyproxy/envoy-wasm,istio/envoy,lyft/envoy,istio/envoy,envoyproxy/envoy-wasm,jrajahalme/envoy,jrajahalme/envoy,eklitzke/envoy,lyft/envoy,jrajahalme/envoy,dnoe/envoy,lizan/envoy,eklitzke/envoy,envoyproxy/envoy,eklitzke/envoy,envoyproxy/envoy,dnoe/envoy,lizan/envoy,envoyproxy/envoy-wasm,lizan/envoy,eklitzke/envoy,istio/envoy,envoyproxy/envoy,lizan/envoy