Restore pod Firebase/Firestore for tvOS (#15127)

Author: paulb777

Firebase.podspec

@@ -128,7 +128,7 @@ Simplify your app development, grow your user base, and monetize more effectivel
     ss.dependency 'FirebaseFirestore', '~> 12.1.0'
     ss.ios.deployment_target = '15.0'
     ss.osx.deployment_target = '10.15'
-    ss.ios.deployment_target = '15.0'
+    ss.tvos.deployment_target = '15.0'
   end
 
   s.subspec 'Functions' do |ss|

Firestore/CHANGELOG.md

@@ -1,3 +1,6 @@
+# Unreleased
+- [fixed] Fixed accidental removal of `pod "Firebase/Firestore"` for tvOS in 12.0.0.
+
 # 11.12.0
 - [fixed] Fixed the `null` value handling in `isNotEqualTo` and `notIn` filters.