Revert "bump NBitcoin version 5.0.41 -> 5.0.49"

This reverts commit 21fb15e,
because:

- There was no motivation for this upgrade (nothing specified
in the commit message).
- It might introduce bugs that we don't want to deal with, at
the moment.
- We might revert this revert shortly after finishing our
milestone4 (closing channels).

src/DotNetLightning.Core/DotNetLightning.Core.fsproj

@@ -98,7 +98,7 @@
   </ItemGroup>
   <ItemGroup>
     <PackageReference Update="FSharp.Core" Version="4.7.0" />
-    <PackageReference Include="NBitcoin" Version="5.0.49" />
+    <PackageReference Include="NBitcoin" Version="5.0.41" />
     <PackageReference Condition="'$(BouncyCastle)' != 'true'" Include="NBitcoin.Secp256k1" Version="1.0.3" />
     <PackageReference Condition="'$(BouncyCastle)'=='true'" Include="Portable.BouncyCastle" Version="1.8.5.2" />
     <PackageReference Include="System.Memory" Version="4.5.3" />