update dockerfile to use pre-release versions of stuff

Author: William Kray

Dockerfile

@@ -5,9 +5,9 @@ FROM node:14-buster as builder
 # images of element-web develop.
 ARG USE_CUSTOM_SDKS=true
 ARG REACT_SDK_REPO="https://github.com/williamkray/matrix-react-sdk.git"
-ARG REACT_SDK_BRANCH="wreck/v3.26.0-wrecked"
+ARG REACT_SDK_BRANCH="wreck/v3.27.0-rc.1-wrecked"
 ARG JS_SDK_REPO="https://github.com/matrix-org/matrix-js-sdk.git"
-ARG JS_SDK_BRANCH="master"
+ARG JS_SDK_BRANCH="release-v12.2.0"
 
 RUN apt-get update && apt-get install -y git dos2unix