Slightly tweak logic (minor; superficial)

Change originally part of: 12e225afef
More information in that commit's message.

themes/base.theme.bash

@@ -181,11 +181,9 @@ function scm_prompt_info_common {
 }
 
 function terraform_workspace_prompt {
-	if _command_exists terraform; then
-		if [ -d .terraform ]; then
+	if _command_exists terraform && [ -d .terraform ]; then
 		echo -e "$(terraform workspace show 2> /dev/null)"
 	fi
-	fi
 }
 
 function git_prompt_minimal_info {