Fix build after swiftlang/swift-docc#1371

(cherry picked from commit b5bc653)

Author: AnthonyLatsis

Sources/DocumentationLanguageService/DocCReferenceResolutionService.swift

@@ -10,6 +10,7 @@
 //
 //===----------------------------------------------------------------------===//
 
+import DocCCommon
 import Foundation
 import IndexStoreDB
 @_spi(SourceKitLSP) import LanguageServerProtocol