More final WebAuthn UX strings.

Most notably, `security key` is no longer capitalized.

Bug: 849323
Change-Id: I5f9693cd95c21d770dbac7d2eeba081b2bf34f1a
Reviewed-on: https://chromium-review.googlesource.com/1179900
Commit-Queue: Balazs Engedy <engedy@chromium.org>
Reviewed-by: Jun Choi <hongjunchoi@chromium.org>
Cr-Commit-Position: refs/heads/master@{#584213}

chrome/browser/ui/webauthn/sheet_models.cc

@@ -248,7 +248,7 @@ base::string16 AuthenticatorBleEnterPairingModeSheetModel::GetStepTitle()
   // TODO(hongjunchoi): Insert actual domain name from model to
   // |application_name|.
   base::string16 application_name = base::UTF8ToUTF16("example.com");
-  return l10n_util::GetStringFUTF16(IDS_WEBAUTHN_GENERIC_TITLE,
+  return l10n_util::GetStringFUTF16(IDS_WEBAUTHN_BLE_ENTER_PAIRING_MODE_TITLE,
                                     application_name);
 }