Remove invalid tests

Author: GeekInTheNorth

src/Stott.Security.Optimizely.Test/Features/CustomHeaders/Repository/CustomHeaderMapperTests.cs

@@ -324,18 +324,6 @@ public void GetAllowedValues_GivenNull_ThenReturnsNull()
         Assert.That(result, Is.Null);
     }
 
-    [Test]
-    [TestCaseSource(typeof(CustomHeaderMapperTestCases), nameof(CustomHeaderMapperTestCases.FixedSelectHeaders))]
-    public void GetAllowedValues_GivenFixedSelectHeader_ThenFirstItemHasEmptyValue(string headerName)
-    {
-        // Act
-        var result = CustomHeaderMapper.GetAllowedValues(headerName);
-
-        // Assert
-        Assert.That(result, Is.Not.Null);
-        Assert.That(result.First().Value, Is.EqualTo(string.Empty));
-    }
-
     [Test]
     public void ToEntity_MapsHeaderNameBehaviorAndValue()
     {