Update static UI assets path in contrib doc (#2548)

Signed-off-by: albertteoh <albert.teoh@logz.io>

CONTRIBUTING.md

@@ -30,22 +30,14 @@ Then install dependencies and run the tests:
 git submodule update --init --recursive
 make install-tools
 make test
-#if you wish to build platform binaries locally - the step below is needed.
+# if you wish to build platform binaries locally - the step below is needed.
 make build-ui
 ```
 
 ### Running local build with the UI
 
-The `jaeger-ui` submodule contains the source code for the UI assets (requires Node.js 6+). The assets must be compiled first with `make build-ui`, which runs Node.js build and then packages the assets into a Go file that is `.gitignore`-ed. The packaged assets can be enabled by providing a build tag `ui`, e.g.:
-
-```
-$ go run -tags ui ./cmd/all-in-one/main.go
-```
-
-Alternatively, the path to the built UI assets can be provided via `--query.static-files` flag:
-
 ```
-$ go run ./cmd/all-in-one/main.go --query.static-files jaeger-ui/build
+$ make run-all-in-one
 ```
 
 ## Project Structure