spelling: existing

Signed-off-by: Josh Soref <jsoref@users.noreply.github.com>

server/api_test.go

@@ -226,7 +226,7 @@ func TestCheckCost(t *testing.T) {
 	}
 }
 
-// Attempts to list and revoke an exisiting refresh token.
+// Attempts to list and revoke an existing refresh token.
 func TestRefreshToken(t *testing.T) {
 	logger := &logrus.Logger{
 		Out:       os.Stderr,