Remove revision from version command

The revision field is only populated on dev builds so this means
most releases of Terraform have an empty "terraform_revision" field
in the JSON output. Since we recommend developers use go tooling
to `go build` this tool when developing, the revision is not useful
data and so it is removed.

main.go

@@ -117,8 +117,8 @@ func wrappedMain() int {
 	}
 
 	log.Printf(
-		"[INFO] Terraform version: %s %s %s",
-		Version, VersionPrerelease, GitCommit)
+		"[INFO] Terraform version: %s %s",
+		Version, VersionPrerelease)
 	log.Printf("[INFO] Go runtime version: %s", runtime.Version())
 	log.Printf("[INFO] CLI args: %#v", os.Args)