Specify Swift Version in Firestore test settings (#14488)

Firestore/Example/Firestore.xcodeproj/project.pbxproj

@@ -5986,6 +5986,7 @@
 				ONLY_ACTIVE_ARCH = YES;
 				OTHER_CFLAGS = "";
 				SDKROOT = iphoneos;
+				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = "1,2";
 				TVOS_DEPLOYMENT_TARGET = 13.0;
 			};
@@ -6035,6 +6036,7 @@
 				OTHER_CFLAGS = "";
 				SDKROOT = iphoneos;
 				SWIFT_COMPILATION_MODE = wholemodule;
+				SWIFT_VERSION = 5.0;
 				TARGETED_DEVICE_FAMILY = "1,2";
 				TVOS_DEPLOYMENT_TARGET = 13.0;
 				VALIDATE_PRODUCT = YES;
@@ -6058,7 +6060,7 @@
 				PRODUCT_BUNDLE_IDENTIFIER = "org.cocoapods.demo.${PRODUCT_NAME:rfc1034identifier}";
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				SWIFT_OPTIMIZATION_LEVEL = "-Onone";
-				SWIFT_VERSION = 4.0;
+				SWIFT_VERSION = 5.9;
 				WRAPPER_EXTENSION = app;
 			};
 			name = Debug;
@@ -6080,7 +6082,7 @@
 				MODULE_NAME = ExampleApp;
 				PRODUCT_BUNDLE_IDENTIFIER = "org.cocoapods.demo.${PRODUCT_NAME:rfc1034identifier}";
 				PRODUCT_NAME = "$(TARGET_NAME)";
-				SWIFT_VERSION = 4.0;
+				SWIFT_VERSION = 5.9;
 				WRAPPER_EXTENSION = app;
 			};
 			name = Release;