fix(build): drop Warp3D's unresolvable OpenMetaverse.Rendering.Meshmerizer 1.0.6 reference

[JohnLegionH]

What breaks

Source/Warp3D/Warp3D.csproj carries

<PackageReference Include="OpenMetaverse.Rendering.Meshmerizer" Version="1.0.6" />

That package resolves from neither source this repository configures. nuget.org
answers 404 for it. The OpenSim-NGC GitHub Packages feed answers 403, using a
token that reads every other NGC package in the tree without trouble - the
UtopiaSkye.* packages restore from the same feed with the same credentials in
the same run.

NuGet fails the restore for the whole solution on it, not just for Warp3D, so a
clean clone of develop cannot be built at all:

dotnet build Tranquillity.sln -c Release
...
    6 Warning(s)
    16 Error(s)

All 16 are NU1301, one per project that reaches Warp3D transitively -
OpenSim.Region.CoreModules, Phlox.ScriptEngine, OpenSim.Server.RegionServer,
OpenSim.Tests.Common and twelve more. A representative pair of lines:

error NU1301: Failed to retrieve information about 'OpenMetaverse.Rendering.Meshmerizer'
  from remote source 'https://nuget.pkg.github.com/OpenSim-NGC/download/openmetaverse.rendering.meshmerizer/index.json'.
error NU1301:   Response status code does not indicate success: 403 (Forbidden).

Measured on develop at f4c4d1efa9 with nothing else changed.

Why the line is redundant

Directory.Build.props already gives every project in the tree the same
component, from the package this organisation actually publishes:

<PackageReference Include="UtopiaSkye.OpenMetaverse.Rendering.Meshmerizer" Version="1.1.7" />

Warp3D's extra reference is an older, differently named copy of it. Nothing in
Source/Warp3D/ is written against an API the 1.1.7 package does not provide,
and no other .csproj or .props in the tree mentions the unprefixed package -
this is its only occurrence.

Result after removal

dotnet restore Tranquillity.sln     -> exit 0
dotnet build Tranquillity.sln -c Release
    0 Error(s)

One line deleted, nothing else touched.

Relationship to the Track L PR

The identical one-line change is also the tip commit of the Track L (AIS v3 +
SSB) pull request, because that branch cannot be built or CI-tested without it;
the two merge clean in either order, and whichever lands second is a no-op.