Fixup dockerfile

Signed-off-by: Oliver Gould <ver@buoyant.io>

Dockerfile

@@ -61,16 +61,7 @@ RUN --mount=type=cache,target=target \
 ## Install the proxy binary into the base runtime image.
 FROM $RUNTIME_IMAGE as runtime
 
-# When set, causes the proxy to remove the identity wrapper responsible for
-# CSR and key generation.
-ARG SKIP_IDENTITY_WRAPPER
-
 WORKDIR /linkerd
 COPY --from=build /out/linkerd2-proxy /usr/lib/linkerd/linkerd2-proxy
 ENV LINKERD2_PROXY_LOG=warn,linkerd=info
-RUN \
-  if [ -n "$SKIP_IDENTITY_WRAPPER" ] ; then \
-    rm -f /usr/bin/linkerd2-proxy-run && \
-    ln /usr/lib/linkerd/linkerd2-proxy /usr/bin/linkerd2-proxy-run ; \
-  fi
 # Inherits the ENTRYPOINT from the runtime image.