Bump the min versions to match what Firebase will do for version 12.

https://github.com/firebase/firebase-ios-sdk/blob/main/FirebaseCore/CHANGELOG.md#unreleased

BUILD.bazel

@@ -89,7 +89,7 @@ macos_unit_test(
 
 ios_unit_test(
     name = "GTMSessionFetcherCoreTests_iOS",
-    minimum_os_version = "13.0",
+    minimum_os_version = "15.0",
     runner = "@rules_apple//apple/testing/default_runner:ios_xctestrun_ordered_runner",
     deps = [":GTMSessionFetcherCoreTestsLib"],
 )
@@ -113,7 +113,7 @@ macos_unit_test(
 
 ios_unit_test(
     name = "GTMSessionFetcherUserAgentTests_iOS",
-    minimum_os_version = "13.0",
+    minimum_os_version = "15.0",
     runner = "@rules_apple//apple/testing/default_runner:ios_xctestrun_ordered_runner",
     target_compatible_with = ["@platforms//os:ios"],
     deps = [":GTMSessionFetcherUserAgentTestsLib"],

GTMSessionFetcher.podspec

@@ -21,9 +21,9 @@ Pod::Spec.new do |s|
   # bundle for the privacy manifest.
   s.cocoapods_version = '>= 1.12.0'
 
-  ios_deployment_target = '13.0'
+  ios_deployment_target = '15.0'
   osx_deployment_target = '10.15'
-  tvos_deployment_target = '13.0'
+  tvos_deployment_target = '15.0'
   visionos_deployment_target = '1.0'
   watchos_deployment_target = '7.0'
 

Package.swift

@@ -1,13 +1,13 @@
-// swift-tools-version:5.3
+// swift-tools-version:5.8
 // The swift-tools-version declares the minimum version of Swift required to build this package.
 import PackageDescription
 
 let package = Package(
     name: "GTMSessionFetcher",
     platforms: [
-        .iOS(.v13),
+        .iOS(.v15),
         .macOS(.v10_15),
-        .tvOS(.v13),
+        .tvOS(.v15),
         .watchOS(.v7)
     ],
     products: [

TestApps/TestApps.xcodeproj/project.pbxproj

@@ -494,11 +494,11 @@
 					../Sources/Core/Public,
 					../Sources/Full/Public,
 				);
-				IPHONEOS_DEPLOYMENT_TARGET = 13.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 15.0;
 				MACOSX_DEPLOYMENT_TARGET = 10.15;
 				ONLY_ACTIVE_ARCH = YES;
 				SDKROOT = macosx;
-				TVOS_DEPLOYMENT_TARGET = 13.0;
+				TVOS_DEPLOYMENT_TARGET = 15.0;
 				WARNING_CFLAGS = (
 					"-Werror",
 					"-Wextra",
@@ -579,10 +579,10 @@
 					../Sources/Core/Public,
 					../Sources/Full/Public,
 				);
-				IPHONEOS_DEPLOYMENT_TARGET = 13.0;
+				IPHONEOS_DEPLOYMENT_TARGET = 15.0;
 				MACOSX_DEPLOYMENT_TARGET = 10.15;
 				SDKROOT = macosx;
-				TVOS_DEPLOYMENT_TARGET = 13.0;
+				TVOS_DEPLOYMENT_TARGET = 15.0;
 				WARNING_CFLAGS = (
 					"-Werror",
 					"-Wextra",