fixed some syntax errors, builds fine now

Freechat/Dockerfile

@@ -1,11 +1,10 @@
-FROM docker pull debian:sid-slim as sid
+FROM debian:sid-slim
 MAINTAINER Alejandro Santillana alejandros714@protonmail.com
 
 # Pre-reqs for sql and building later on
 RUN apt-get update && apt-get install -y curl libmysqlclient-dev build-essential
 
 # Installing Nightly version of Rust as mysql_async requires it
-RUN
 RUN curl --proto '=https' --tlsv1.2 -sSf https://sh.rustup.rs | \
 	sh -s -- -y --default-toolchain nightly-2020-01-24