…tically (#18068)

#### Why I did it
src/sonic-sairedis
```
* a504933 - (HEAD -> master, origin/master, origin/HEAD) Change dash API pipeline name (#1351) (11 hours ago) [Kamil Cudnik]
```
#### How I did it
#### How to verify it
#### Description for the changelog

…se on Arista 7280DR3A variants (sonic-net#1351)

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#### Why I did it
Arista 7280DR3A SKUs don't support controlling thermal and psu fan speed. This makes some platform_tests under sonic-mgmt fail since they assume they are controllable by default.

Tests affected by this:

`platform_tests/api/test_psu_fans.py::TestPsuFans::test_set_fans_speed`
`platform_tests/api/test_thermal.py::TestThermalApi::test_set_low_threshold`
`platform_tests/api/test_thermal.py::TestThermalApi::test_set_high_threshold`

##### Work item tracking
- Microsoft ADO **(number only)**:

#### How I did it
Modify `platform.json` to explicity mention that psu fan speed and thermal sensors are not controllable

#### How to verify it
Reran the above-mentioned tests and verified that they are skipped.

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#### Which release branch to backport (provide reason below if selected)

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- [x] 202503 (For Disagg T2)

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- [x] msft-202503

#### Description for the changelog
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