Fix a bug that prevents a new shell from being opened in theia. The immediate cause is that the PATH of the shell process is overwritten (it then only contains the path of go), which caused the script that launches the shell to crash because is relied on the env command being in the PATH.

This first rewrites the shell script without using env, so that the shell should be able to start even if the PATH is completely broken.

Further investigation shows that the overwritten PATH seems to be caused by the golang.go extension. So this then removes the golang.go extension from the ones installed by default.

EDIT: to reproduce the bug simply create a .go file and open it in the theia editor.