Remove PIN placeholder text

It's not always 6 digits, so it's a confusing placeholder

// FREEBIE

Signal/src/ViewControllers/OWS2FASettingsViewController.m

@@ -113,8 +113,6 @@ NS_ASSUME_NONNULL_BEGIN
 {
     self.pinTextfield = [UITextField new];
     self.pinTextfield.textColor = [UIColor blackColor];
-    self.pinTextfield.placeholder
-        = NSLocalizedString(@"2FA_PIN_DEFAULT_TEXT", @"Text field placeholder when entering a 'two-factor auth pin'.");
     self.pinTextfield.font = [UIFont ows_mediumFontWithSize:ScaleFromIPhone5To7Plus(30.f, 36.f)];
     self.pinTextfield.textAlignment = NSTextAlignmentCenter;
     self.pinTextfield.keyboardType = UIKeyboardTypeNumberPad;

Signal/src/views/PinEntryView.m

@@ -61,8 +61,6 @@ NS_ASSUME_NONNULL_BEGIN
 {
     self.pinTextfield = [UITextField new];
     self.pinTextfield.textColor = [UIColor blackColor];
-    self.pinTextfield.placeholder
-        = NSLocalizedString(@"2FA_PIN_DEFAULT_TEXT", @"Text field placeholder when entering a 'two-factor auth pin'.");
     self.pinTextfield.font = [UIFont ows_mediumFontWithSize:ScaleFromIPhone5To7Plus(30.f, 36.f)];
     self.pinTextfield.textAlignment = NSTextAlignmentCenter;
     self.pinTextfield.keyboardType = UIKeyboardTypeNumberPad;

Signal/translations/en.lproj/Localizable.strings

@@ -1,6 +1,3 @@
-/* Text field placeholder when entering a 'two-factor auth pin'. */
-"2FA_PIN_DEFAULT_TEXT" = "••••••";
-
 /* Button text to dismiss missing contacts permission alert */
 "AB_PERMISSION_MISSING_ACTION_NOT_NOW" = "Not Now";