set proper version

Dockerfile

@@ -2,12 +2,12 @@ from ubuntu:latest
 
 MAINTAINER [email protected]
 
-ENV GAMBIT_VERSION 4.9.1
+ENV GAMBIT_VERSION v4.9.1
 RUN apt update -y
 RUN apt install -y libsqlite3-dev build-essential git autoconf libsnappy1v5 libleveldb1v5 zlib1g-dev libssl-dev pkg-config  libyaml-dev libmysqlclient-dev liblmdb-dev libleveldb-dev rsync texinfo
 
 RUN git config --global url.https://github.com/.insteadOf git://github.com/
-RUN cd /root && git clone https://github.com/gambit/gambit && cd /root/gambit && git fetch -a && git checkout v${GAMBIT_VERSION}
+RUN cd /root && git clone https://github.com/gambit/gambit && cd /root/gambit && git fetch -a && git checkout ${GAMBIT_VERSION}
 
 RUN cd /root/gambit && ./configure --prefix=/usr/local/gambit --enable-single-host --enable-openssl --enable-default-runtime-options=f8,-8,t8 --enable-poll
 RUN cd /root/gambit && make -j4