refactor: removes unnecessary exception message assertions

These messages differ between .NET Framework, .NET Standard and .NET 8, making them tedious to test. The messages themselves are superfluous and unnecessary for what we're doing, so the assertions have been removed.

ShopifySharp.Tests/Infrastructure/Serialization/Json/SystemJsonSerializerTests.cs

@@ -218,7 +218,6 @@ public void Deserialize_WhenTheNodeIsNotASystemTextJsonNode_ShouldThrow()
         // Assert
         act.Should()
             .Throw<ArgumentException>()
-            .WithMessage($"Expected a {nameof(SystemJsonElement)} but got *. (Parameter 'element')")
             .And
             .ParamName
             .Should()
@@ -305,7 +304,6 @@ public void Deserialize_T_WhenTheNodeIsNotASystemTextJsonNode_ShouldThrow()
         // Assert
         act.Should()
             .Throw<ArgumentException>()
-            .WithMessage($"Expected a {nameof(SystemJsonElement)} but got *. (Parameter 'element')")
             .And
             .ParamName
             .Should()
@@ -378,8 +376,7 @@ public async Task DeserializeAsync_WhenTheNodeIsNotASystemTextJsonNode_ShouldThr
 
         // Assert
         var exn = await act.Should()
-            .ThrowAsync<ArgumentException>()
-            .WithMessage($"Expected a {nameof(SystemJsonElement)} but got *. (Parameter 'element')");
+            .ThrowAsync<ArgumentException>();
         exn.And.ParamName.Should().Be("element");
     }
 
@@ -458,8 +455,7 @@ public async Task DeserializeAsync_T_WhenTheNodeIsNotASystemTextJsonNode_ShouldT
 
         // Assert
         var exn = await act.Should()
-            .ThrowAsync<ArgumentException>()
-            .WithMessage($"Expected a {nameof(SystemJsonElement)} but got *. (Parameter 'element')");
+            .ThrowAsync<ArgumentException>();
         exn.And.ParamName.Should().Be("element");
     }