[cmake] Remove dependency on PackageModelSyntax library

This is a follow-up to #2235.

The change removed uses of `PackageModelSyntax` but left is in
`target_link_libraries` of `SourceKitLSP`.

Author: xedin

Sources/SwiftLanguageService/CMakeLists.txt

@@ -74,7 +74,6 @@ target_link_libraries(SourceKitLSP PRIVATE
   Crypto
   TSCBasic
   PackageModel
-  PackageModelSyntax
   SwiftSyntax::SwiftDiagnostics
   SwiftSyntax::SwiftIDEUtils
   SwiftSyntax::SwiftParser