chore: delete obsolete C++ file

src/Lean/ProjFns.lean

@@ -36,13 +36,11 @@ def ProjectionFunctionInfo.fromClassEx (info : ProjectionFunctionInfo) : Bool :=
 
 builtin_initialize projectionFnInfoExt : MapDeclarationExtension ProjectionFunctionInfo ← mkMapDeclarationExtension
 
-@[export lean_add_projection_info]
 def addProjectionFnInfo (env : Environment) (projName : Name) (ctorName : Name) (numParams : Nat) (i : Nat) (fromClass : Bool) : Environment :=
   projectionFnInfoExt.insert env projName { ctorName, numParams, i, fromClass }
 
 namespace Environment
 
-@[export lean_get_projection_info]
 def getProjectionFnInfo? (env : Environment) (projName : Name) : Option ProjectionFunctionInfo :=
   projectionFnInfoExt.find? env projName
 

src/library/CMakeLists.txt

@@ -3,7 +3,6 @@ add_library(library OBJECT expr_lt.cpp
   module.cpp dynlib.cpp replace_visitor.cpp num.cpp
   class.cpp util.cpp print.cpp annotation.cpp
   reducible.cpp init_module.cpp
-  projection.cpp
   aux_recursors.cpp
   profiling.cpp time_task.cpp
   formatter.cpp

src/library/util.cpp

@@ -17,7 +17,6 @@ Author: Leonardo de Moura
 #include "library/suffixes.h"
 #include "library/annotation.h"
 #include "library/constants.h"
-#include "library/projection.h"
 #include "library/replace_visitor.h"
 #include "library/num.h"
 #include "githash.h" // NOLINT