Pin explicit Swift version on UI test target for build consistency

Author: sinoru

PatronArchiver.xcodeproj/project.pbxproj

@@ -559,6 +559,7 @@
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				STRING_CATALOG_GENERATE_SYMBOLS = NO;
 				SWIFT_EMIT_LOC_STRINGS = NO;
+				SWIFT_VERSION = 5.0;
 				TEST_TARGET_NAME = PatronArchiver;
 			};
 			name = Debug;
@@ -571,6 +572,7 @@
 				PRODUCT_NAME = "$(TARGET_NAME)";
 				STRING_CATALOG_GENERATE_SYMBOLS = NO;
 				SWIFT_EMIT_LOC_STRINGS = NO;
+				SWIFT_VERSION = 5.0;
 				TEST_TARGET_NAME = PatronArchiver;
 			};
 			name = Release;