terraform: disable terraform prompt in $HOME (#7227)

In the home directory there is a .terraform folder for modules but it is most likely not
an actual directory of terraform scripts. Therefore, this patch disables checking for workspace in the home directory.

plugins/terraform/terraform.plugin.zsh

 function tf_prompt_info() {
+    # dont show 'default' workspace in home dir
+    [[ "$PWD" == ~ ]] && return
     # check if in terraform dir
     if [ -d .terraform ]; then
       workspace=$(terraform workspace show 2> /dev/null) || return