replace hardcoded registry with reference to registry

Author: lilachic

README.md

@@ -32,7 +32,7 @@ You can provide argument variables to change which library versions get built.
 
 `emscripten`, `libsodium`, and `openssl` versions can be changed with `--build-arg` by changing the value of `EMSCRIPTEN_VERSION`, `LIBSODIUM_VERSION`, `EMSDK_IMAGE` and `OPENSSL_VERSION`.
 
->__NOTE:__ To build only ARM images use -arm in version tag and for ARM built images. For example `EMSDK_IMAGE --build-arg="EMSDK_IMAGE=sds-docker-local.artifactory.ci.csc.fi/sd-connect/emscripten/emsdk"  --build-arg="EMSCRIPTEN_VERSION=3.1.21-arm"` instructs to use locally build emsdk:3.1.21-arm container. 
+>__NOTE:__ To build only ARM images use -arm in version tag and for ARM built images. For example `EMSDK_IMAGE --build-arg="EMSDK_IMAGE=<local-registry>/emscripten/emsdk"  --build-arg="EMSCRIPTEN_VERSION=3.1.21-arm"` instructs to use locally build emsdk:3.1.21-arm container. 
 
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