gopls/internal/server: modify return of parseAction

Given that T is always a string type, return "" instead.

Change-Id: I1959b8941e24deb2ab52b342e17b0e4535297389
Reviewed-on: https://go-review.googlesource.com/c/tools/+/797500
LUCI-TryBot-Result: golang-scoped@luci-project-accounts.iam.gserviceaccount.com <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Ethan Lee <ethanalee@google.com>
Reviewed-by: Alan Donovan <adonovan@google.com>

gopls/internal/server/vulncheck_prompt.go

diff --git a/gopls/internal/server/vulncheck_prompt.go b/gopls/internal/server/vulncheck_prompt.go
index 3c21a04..cd71c73 100644
--- a/gopls/internal/server/vulncheck_prompt.go
+++ b/gopls/internal/server/vulncheck_prompt.go
@@ -410,14 +410,14 @@
 
 // parseAction parses s against the list of allowed actions case-insensitively.
 // It returns the matching action and true if a match is found.
-// Otherwise, it returns the zero value of T and false.
+// Otherwise, it returns "" and false.
 func parseAction[T ~string](s string, actions []T) (T, bool) {
 	for _, a := range actions {
 		if strings.EqualFold(string(a), s) {
 			return a, true
 		}
 	}
-	return *new(T), false
+	return "", false
 }
 
 func getVulncheckPreference() (vulncheckAction, error) {