internal/scan: remove obsolete function

Removes the "fileExists" function which is no longer used.

Fixes golang/go#63967

Change-Id: I7ac9eb5537f4419c22774a43ba955d2191c2fe84
Reviewed-on: https://go-review.googlesource.com/c/vuln/+/540195
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Auto-Submit: Maceo Thompson <maceothompson@google.com>
Reviewed-by: Zvonimir Pavlinovic <zpavlinovic@google.com>

internal/scan/flags.go

@@ -5,7 +5,6 @@
 package scan
 
 import (
-	"errors"
 	"flag"
 	"fmt"
 	"io"
@@ -166,20 +165,6 @@ func isFile(path string) bool {
 	return !s.IsDir()
 }
 
-// fileExists checks if file path exists. Returns true
-// if the file exists or it cannot prove that it does
-// not exist. Otherwise, returns false.
-func fileExists(path string) bool {
-	if _, err := os.Stat(path); err == nil {
-		return true
-	} else if errors.Is(err, os.ErrNotExist) {
-		return false
-	}
-	// Conservatively return true if os.Stat fails
-	// for some other reason.
-	return true
-}
-
 type showFlag []string
 
 func (v *showFlag) Set(s string) error {