[genio] Update platform_maintainers.yaml (#73032)

* [genio] Update platform_maintainers.yaml

Update MediaTek maintainers and paths in platform_maintainers.yaml

* [genio] Update the MediaTek entry in `platform_maintainers.yaml` to reflect the current team ownership

### Summary

Update the MediaTek entry in `platform_maintainers.yaml` to reflect the current team ownership:

- Refreshed the list of MediaTek maintainers (added/removed reviewers as per current team composition).
- Updated the `paths` glob(s) so that MediaTek-owned directories are correctly routed to the new maintainer set for review assignment.

This keeps CODEOWNERS-style auto-review requests aligned with the actual engineers responsible for the MediaTek platform code, avoiding stale review assignments to inactive members.

### Related issues

N/A — routine maintainer roster update, no functional code change.

### Testing

- Verified YAML syntax is valid (file parses without error).
- Confirmed the updated `paths` patterns match the intended MediaTek platform directories.
- No source/build code touched; no unit or integration tests required.

* [genio] Use vendor name in platform_maintainers.yaml for consistency

[genio] Use vendor name in platform_maintainers.yaml for consistency

Replace platform name "mt793x" with vendor name "mediatek" to match
the file's convention of keying entries by vendor.

---------

Co-authored-by: Andrei Litvin <andy314@gmail.com>

.github/platform_maintainers.yaml

diff --git a/.github/platform_maintainers.yaml b/.github/platform_maintainers.yaml
index 4d8d02c..2a1ff78 100644
--- a/.github/platform_maintainers.yaml
+++ b/.github/platform_maintainers.yaml
@@ -83,6 +83,15 @@
     - "config/ameba/**"
     - "scripts/tools/realtek/**"
 
+mediatek:
+  maintainers:
+    - RyanHo-MTK
+    - as23999
+  paths:
+    - "src/platform/mt793x/**"
+    - "examples/lighting-app/genio/**"
+    - "third_party/mt793x_sdk/**"
+
 stm32:
   maintainers:
     - STYoannZamaron
@@ -161,13 +170,6 @@
 #   paths:
 #     - "src/platform/webos/**"
 # 
-# mt793x:
-#   maintainers:
-#     - pakls
-#   paths:
-#     - "src/platform/mt793x/**"
-#     - "examples/platform/mt793x/**"
-# 
 # ti:
 #   maintainers:
 #     - s-jain2022