Nullability removed when creating anonymous type

**Version Used**:

```
$ dotnet --version
10.0.201
```

**Steps to Reproduce**:

Repro: https://lab.razor.fyi/#fY9BSwMxEIXp3jI3exLxMOSk0IZkoQVZREQvCop4FcEY0yWyJiXJbpUlf8R_4L-UDdUtHrwMj_e9x8zAVwFw513t5RtTYfpZgGpkCLj1oAdExBBlNAo7Z17wRhp7dJztHggJ0Rtb48PjGdq2ac69lx94mnX1B7vb3YDe4C_EHumlfm5rOkN6rxstg6aYKgBCOulx7d2rVvHKrlzYdocSEEIGnQW5cHZl6tbLaJzNsZ91s4GnPP-Lj_eNhVTlTxMkmO4t2JLxecnKpVicMCHKg33BGWd8vva6M3ozEnooBONM8B020utChafJ--Qb

Sample code:

```cs
string []? nullArray = null;
string []? noNullArray = new string [] { "Debug", "Release" };

var projectInfos = new [] {
new {
Configurations = nullArray,
},
new {
Configurations = noNullArray,
},
};
```

**Expected Behavior**:

No warning

**Actual Behavior**:

> warning CS8619: Nullability of reference types in value of type '' doesn't match target type ''.

It seems the nullable `noNullArray` ends up being a non-nullable type at some point, causing a type mismatch in the anonymous type.