Update dependency firebase/firebase-ios-sdk to v12

Author: renovate[bot]

Package.swift

@@ -17,7 +17,7 @@ let package = Package(
  ],
  dependencies: [
  .package(url: "https://github.com/fumito-ito/FunctionCalling", from: "0.5.0"),
- .package(url: "https://github.com/firebase/firebase-ios-sdk.git", from: "11.15.0")
+ .package(url: "https://github.com/firebase/firebase-ios-sdk.git", from: "12.1.0")
  ],
  targets: [
  // Targets are the basic building blocks of a package, defining a module or a test suite.