constraint_solver: remove ToInt64Vector from .Net wrapper

note: already NOT available in python and java

Author: Mizux

ortools/constraint_solver/csharp/ConstraintSolverTests.cs

@@ -20,17 +20,6 @@ namespace Google.OrTools.Tests
 {
 public class ConstraintSolverTest
 {
-    [Fact]
-    public void IntVectorToInt64Vector()
-    {
-        int[] input = { 5, 11, 17 };
-        long[] output = ToInt64Vector(input);
-        Assert.Equal(3, output.Length);
-        Assert.Equal(5, output[0]);
-        Assert.Equal(11, output[1]);
-        Assert.Equal(17, output[2]);
-    }
-
     [Fact]
     public void IntVarConstructor()
     {

ortools/constraint_solver/csharp/constraint_solver.i

@@ -234,6 +234,10 @@ DEFINE_ARGS_TO_R_CALLBACK(
 // Renaming
 namespace operations_research {
 
+// This method causes issues with our std::vector<int64_t> wrapping. It's not really
+// part of the public API anyway.
+%ignore ToInt64Vector;
+
 // Decision
 %feature("director") Decision;
 %unignore Decision;