[filesys/miniFilter/delete]: Potential FLT_CONTEXT leak issue

@jrixie is already working on this.

Since Apr 28, 2026.

### Which is the area where the sample lives?

/filesys/miniFilter/

### Describe the issue

I set the `StartType` to 1 (`SERVICE_SYSTEM_START`). After installing the sample driver and rebooting the system:

In `DfPostCreateCallback`, if `Data->Iopb->TargetFileObject->FileName` is `"\pagefile.sys"` or `"\swapfile.sys"`, the call to `DfGetOrSetContext` returns error `0xC00000BB` (`STATUS_NOT_SUPPORTED`).

In this scenario, `FltReleaseContext` is not called to release the `streamContext` in either `DfPostCreateCallback` or `DfGetOrSetContext`. This causes the driver to fail to unload properly.

Checking with the WinDbg command `!fltkd.filter 8 1` shows that two `FLT_CONTEXT` references remain unreleased:
```
Object usage/reference information:
References to FLT_CONTEXT : 2
Allocations of FLT_CALLBACK_DATA : 0
Allocations of FLT_DEFERRED_IO_WORKITEM : 0
Allocations of FLT_GENERIC_WORKITEM : 0
References to FLT_FILE_NAME_INFORMATION : 0
Open files : 0
References to FLT_OBJECT : 0
List of objects used/referenced::
FLT_VERIFIER_OBJECT: ffffb289c1607b90
Object: ffffe688e6d6d620 Type: FLT_CONTEXT RefCount: 00000001
FLT_VERIFIER_OBJECT: ffffb289c16072f0
Object: ffffe688e6d6f4c0 Type: FLT_CONTEXT RefCount: 00000001
```

Relevant code locations:
[delete.inf#L95](https://github.com/microsoft/Windows-driver-samples/blob/main/filesys/miniFilter/delete/delete.inf#L95)
[delete.c#L2716](https://github.com/microsoft/Windows-driver-samples/blob/main/filesys/miniFilter/delete/delete.c#L2716)
[delete.c#L1241](https://github.com/microsoft/Windows-driver-samples/blob/main/filesys/miniFilter/delete/delete.c#L1241)
[delete.c#L2742](https://github.com/microsoft/Windows-driver-samples/blob/main/filesys/miniFilter/delete/delete.c#L2742)