Docs: corrected outdated command (#12110)
Docs: corrected outdated command (#12110)

Corrected the command to build an envoy docker image from source.
Additional Description: N/A
Risk Level: N/A
Testing: N/A
Docs Changes: Building an Envoy Docker image - Updated step 2
Release Notes: N/A

Signed-off-by: Yosry Ahmed <3599f67f56156056813a0e73d9d7e13242635ac3@google.com>
lizan/envoy,lizan/envoy,envoyproxy/envoy,lyft/envoy,lizan/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,envoyproxy/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy,lizan/envoy,envoyproxy/envoy,lyft/envoy,envoyproxy/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy-wasm,envoyproxy/envoy,lizan/envoy,lyft/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy-wasm,envoyproxy/envoy,lizan/envoy,lyft/envoy,envoyproxy/envoy-wasm,envoyproxy/envoy,lyft/envoy