bump swift tools version

Author: morganchen12

.github/workflows/auth.yml

@@ -29,7 +29,7 @@ jobs:
       matrix:
         podspec: [FirebaseAuthInterop.podspec, FirebaseAuth.podspec]
         target: [ios, tvos, macos --skip-tests, watchos]
-        os: [macos-14]
+        os: [macos-15]
         xcode: [Xcode_16.2]
     runs-on: ${{ matrix.os }}
     steps:
@@ -108,12 +108,6 @@ jobs:
     strategy:
       matrix:
         include:
-          - os: macos-13
-            xcode: Xcode_15.2
-            target: iOS spm
-          - os: macos-14
-            xcode: Xcode_15.4
-            target: iOS spm
           - os: macos-15
             xcode: Xcode_16.2
             target: iOS spm

Package.swift

@@ -1,4 +1,4 @@
-// swift-tools-version:5.9
+// swift-tools-version:6.0
 // The swift-tools-version declares the minimum version of Swift required to
 // build this package.