Whitespace in property names not issuing error

### Issue Description

It seems like changes in https://github.com/dotnet/msbuild/pull/5672 were reverted. Using `$( FOO )` in condition no longer raises an error.

### Steps to Reproduce

```sh
$ cat > foo.proj <

test

EOF

$ dotnet build foo.proj -v:d
Restore complete (0,0s)
foo succeeded (0,0s)
Foo: 'test' and with whitespace: ''
```

### Expected Behavior

Expected error `MSB4259: Unexpected space at position "{1}" of condition "{0}". Did you forget to remove a space?`.

### Actual Behavior

There was no error.

### Analysis

_No response_

### Versions & Configurations

```sh
$ dotnet --info
.NET SDK:
Version: 10.0.100-rc.1.25414.111
Commit: f8a57b66e6
Workload version: 10.0.100-manifests.2f8afce5
MSBuild version: 17.15.0-preview-25414-111+f8a57b66e

Runtime Environment:
OS Name: Mac OS X
OS Version: 15.6
OS Platform: Darwin
RID: osx-arm64
Base Path: /Users/adeel/.dotnet10/sdk/10.0.100-rc.1.25414.111/
```