Undo optimisim around requiring clangd during testing

While the toolchains build clangd now, not all the bots are building it,
so we cannot require it yet.

Author: benlangmuir

Tests/SourceKitTests/LocalClangTests.swift

@@ -20,7 +20,7 @@ import XCTest
 final class LocalClangTests: XCTestCase {
 
   /// Whether to fail tests if clangd cannot be found.
-  static let requireClangd: Bool = true
+  static let requireClangd: Bool = false // Note: Swift CI doesn't build clangd on all jobs
 
   /// Whether clangd exists in the toolchain.
   var haveClangd: Bool = false