fix(deps): Update dependency grpcio to v1.68.0 (#132)

This PR contains the following updates:

| Package | Update | Change |
|---|---|---|
| [grpcio](https://grpc.io) ([source](https://togithub.com/grpc/grpc)) | minor | `==1.67.1` -> `==1.68.0` |

---

### Release Notes

<details>
<summary>grpc/grpc (grpcio)</summary>

### [`v1.68.0`](https://togithub.com/grpc/grpc/releases/tag/v1.68.0)

[Compare Source](https://togithub.com/grpc/grpc/compare/v1.67.1...v1.68.0)

This is release 1.68.0 ([groovy](https://togithub.com/grpc/grpc/blob/master/doc/g_stands_for.md)) of gRPC Core.

For gRPC documentation, see [grpc.io](https://grpc.io/). For previous releases, see [Releases](https://togithub.com/grpc/grpc/releases).

This release contains refinements, improvements, and bug fixes, with highlights listed below.

## Core

-   \[XdsClient]\[Backport] Add missing authority to XdsClient metrics scope ([#&#8203;38009](https://togithub.com/grpc/grpc/issues/38009)). ([#&#8203;38023](https://togithub.com/grpc/grpc/pull/38023))
-   \[Release] Bump core version in preparation for 1.68 Branch Cut. ([#&#8203;37941](https://togithub.com/grpc/grpc/pull/37941))
-   \[ConfigFetcher] Set HTTP2 error to NO_ERROR to do graceful GOAWAYs. ([#&#8203;37939](https://togithub.com/grpc/grpc/pull/37939))
-   \[ruby] reduce INFO log for server CQ pluck registration to DEBUG. ([#&#8203;37633](https://togithub.com/grpc/grpc/pull/37633))
-   \[EventEngine] Enable the PosixEventEngine client experiment. ([#&#8203;35985](https://togithub.com/grpc/grpc/pull/35985))
-   \[chttp2\_server] Fix race between connection starting and it being orphaned. ([#&#8203;37683](https://togithub.com/grpc/grpc/pull/37683))
-   \[Chttp2Server] Fix race between connection manager updates and handshake. ([#&#8203;37772](https://togithub.com/grpc/grpc/pull/37772))
-   \[xds] Fix XdsClient race between ResourceDoesNotExist timer and receiving resources. ([#&#8203;37678](https://togithub.com/grpc/grpc/pull/37678))

## C++

-   \[Build] Minimum version of MSVC is now 2022. ([#&#8203;37687](https://togithub.com/grpc/grpc/pull/37687))
-   \[Build] Bumped the minimum version of cmake. ([#&#8203;37702](https://togithub.com/grpc/grpc/pull/37702))

## Python

-   Add templating and support for Python 3.13. ([#&#8203;37643](https://togithub.com/grpc/grpc/pull/37643))

</details>

---

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requirements.txt

@@ -1,6 +1,6 @@
 black==24.10.0
 grpcio-tools==1.67.1
-grpcio==1.67.1
+grpcio==1.68.0
 protobuf==5.28.3
 pyarrow==18.0.0
 pytest==8.3.3