.gitpod-setup-trac-remote.sh: Restore 'git remote remove trac'

Author: Matthias Koeppe

.gitpod-setup-trac-remote.sh

@@ -3,6 +3,8 @@
 # Exit on error
 set -e
 
+git remote remove trac 2> /dev/null || true  # might still exists from a previous run/prebuild
+
 # Setup trac as remote
 git remote add trac https://github.com/sagemath/sagetrac-mirror.git -t master -t develop
 git remote set-url --push trac no-pushing--this-is-a-read-only-archive