Add pragmas as needed in Internal.Conversions

Some files already used nullable reference types. They don't need disable annotations pragma.

src/Oakton/Internal/Conversion/Conversions.cs

@@ -7,9 +7,10 @@ namespace Oakton.Internal.Conversion;
 
 public class Conversions
 {
+#nullable disable annotations // FIXME
     private readonly LightweightCache<Type, Func<string, object>> _convertors;
     private readonly IList<IConversionProvider> _providers = new List<IConversionProvider>();
-
+#nullable restore
 
     public Conversions()
     {

src/Oakton/Internal/Conversion/DateTimeConverter.cs

@@ -5,6 +5,8 @@
 
 namespace Oakton.Internal.Conversion;
 
+#nullable disable annotations // FIXME
+
 public class DateTimeConverter
 {
     public const string TODAY = "TODAY";

src/Oakton/Internal/Conversion/TimeSpanConverter.cs

@@ -4,6 +4,8 @@
 
 namespace Oakton.Internal.Conversion;
 
+#nullable disable annotations // FIXME
+
 public class TimeSpanConverter
 {
     private const string TimespanPattern =