Fix indentation

Author: weliveindetail

Tests/SwiftFormatPerformanceTests/WhitespaceLinterPerformanceTests.swift

@@ -7,8 +7,8 @@ import XCTest
 final class WhitespaceLinterPerformanceTests: DiagnosingTestCase {
   func testWhitespaceLinterPerformance() {
     #if os(Windows)
-      // https://github.com/swiftlang/swift-format/issues/939
-      throw XCTSkip("This test is flaky on Windows")
+    // https://github.com/swiftlang/swift-format/issues/939
+    throw XCTSkip("This test is flaky on Windows")
     #endif
     let input = String(
       repeating: """