Use better SemVer requirement for WordPressAuthenticator pod

See discussion at
#19163 (comment)

Author: mokagio

Podfile

@@ -222,7 +222,7 @@ abstract_target 'Apps' do
 
   pod 'Gridicons', '~> 1.1.0'
 
-  pod 'WordPressAuthenticator', '~> 2.1.0'
+  pod 'WordPressAuthenticator', '~> 2.1'
   # pod 'WordPressAuthenticator', :git => 'https://github.com/wordpress-mobile/WordPressAuthenticator-iOS.git', :branch => ''
   # pod 'WordPressAuthenticator', :git => 'https://github.com/wordpress-mobile/WordPressAuthenticator-iOS.git', :commit => ''
   # pod 'WordPressAuthenticator', :path => '../WordPressAuthenticator-iOS'

Podfile.lock

@@ -603,7 +603,7 @@ DEPENDENCIES:
   - Starscream (= 3.0.6)
   - SVProgressHUD (= 2.2.5)
   - WordPress-Editor-iOS (~> 1.19.8)
-  - WordPressAuthenticator (~> 2.1.0)
+  - WordPressAuthenticator (~> 2.1)
   - WordPressKit (~> 4.57.0)
   - WordPressShared (~> 1.18.0)
   - WordPressUI (~> 1.12.5)
@@ -884,6 +884,6 @@ SPEC CHECKSUMS:
   ZendeskSupportSDK: 3a8e508ab1d9dd22dc038df6c694466414e037ba
   ZIPFoundation: ae5b4b813d216d3bf0a148773267fff14bd51d37
 
-PODFILE CHECKSUM: 6de269c9c15437b272a025a41941e8d00de0e6d0
+PODFILE CHECKSUM: b04afabe26bbaa890ee18a5c48d3b5faf73b8ebb
 
 COCOAPODS: 1.11.2