[action] [PR:15948] test_cpu_memory_usage.py update memory threshold for 4600 and 2700

[mssonicbld]

Description of PR

Summary:
Fixes # (issue)
29844233

Type of change

• Bug fix
• Testbed and Framework(new/improvement)
• Test case(new/improvement)

Back port request

• 202012
• 202205
• 202305
• 202311
• 202405

Approach

What is the motivation for this PR?

Memory usage is increasing due to more and more feature introduced in new image.
sonic-net/sonic-buildimage#19828

How did you do it?

Modify the lower memory device memory threshold

How did you verify/test it?

https://elastictest.org/scheduler/testplan/675659228c6a916fb2ed5f4e
https://elastictest.org/scheduler/testplan/6756592f083d896c5b8ad5d9
https://elastictest.org/scheduler/testplan/67565a7c083d896c5b8ad5dd
https://elastictest.org/scheduler/testplan/67565aa7dee125b47d881e31

Any platform specific information?

Low memory device

Supported testbed topology if it's a new test case?

Documentation

[mssonicbld]

/azp run

[mssonicbld]

Original PR: #15948

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