[cmake] Remove dependency on PackageModelSyntax library

This is a follow-up to swiftlang#2235.

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

Author: xedin

Sources/SourceKitLSP/CMakeLists.txt

@@ -99,7 +99,6 @@ target_link_libraries(SourceKitLSP PUBLIC
   SwiftSyntax::SwiftRefactor
   SwiftSyntax::SwiftSyntax)
 target_link_libraries(SourceKitLSP PRIVATE
-  PackageModelSyntax
   TSCExtensions
   $<$<NOT:$<PLATFORM_ID:Darwin>>:FoundationXML>)