.Net: Address vulnerable packages (+Update MsGraph for latest Major V5) - #12962

…5) (microsoft#12962)

### Motivation and Context

This PR addresses a recent vulnerability warning received while working
in the Semantic Kernel solution, limited to specific packages for
Prompty, Milvus and Microsoft Graph Plugin.

As part of addressing the vulnerabilities was also necessary to upgrade
the logic to use the newest packages from Microsoft.Graph library.

…ion (microsoft#14715)

### Motivation and Context

A full link-integrity scan of the repository's README files found 13
dead internal links in 4 files. The underlying sample files were deleted
or moved by recent refactors (planner removal microsoft#12399, MEVD Preview 2
microsoft#11028, MsGraph V5 update microsoft#12962, and the Gemini thinking-budget sample
rename in microsoft#13396), but the README entries still point at the old paths.

### Description

- **dotnet/samples/Concepts/README.md**
- `Google_GeminiChatCompletionWithThinkingBudget` -> renamed sample
`Google_GeminiChatCompletionWithThinking` (renamed in microsoft#13396)
- Removed the `VectorStore_DataIngestion_CustomMapper` entry (sample
deleted in microsoft#11028, no replacement)
- Removed the entire `Planners` section (all three samples deleted in
microsoft#12399)
- Removed `MsGraph_ContactsPlugin` / `MsGraph_DrivePlugin` /
`MsGraph_TasksPlugin` entries (no longer present after the MsGraph V5
update in microsoft#12962)
- Removed `WithFunctionCallingStepwisePlanner` entry (deleted together
with the planners in microsoft#12399)
- **dotnet/samples/Demos/OnnxSimpleRAG/README.md**
- Vector Store abstractions link ->
[Microsoft.Extensions.VectorData.Abstractions in
dotnet/extensions](https://github.com/dotnet/extensions/tree/main/src/Libraries/Microsoft.Extensions.VectorData.Abstractions)
(the `dotnet/src/VectorData/VectorData.Abstractions` README itself
points there)
- `InMemoryVectorStore` -> [CommunityToolkit/AI
MEVD/src/InMemory/InMemoryVectorStore.cs](https://github.com/CommunityToolkit/AI/blob/main/MEVD/src/InMemory/InMemoryVectorStore.cs)
(same pointer as `dotnet/src/VectorData/InMemory/README.md`)
- **python/semantic_kernel/connectors/memory_stores/redis/README.md**
- .NET README link -> `dotnet/src/VectorData/Redis/README.md` (current
in-repo location, which forwards to the CommunityToolkit repository)
- **python/samples/concepts/README.md**
- Search section link -> `python/semantic_kernel/connectors/search.py`
(the `connectors/search` directory no longer exists; search now lives in
`search.py`)

### Verification

All 5 new URLs were checked and return HTTP 200. All 13 removed/updated
links were verified to return HTTP 404 against `main` before this
change.

Docs-only change: no code is touched, so builds and unit tests are
unaffected.