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Reduce Metrics Server memory requirement

**What this PR does / why we need it**:
Reduces memory requirements of Metrics Server.

This was tested on GCE. On 16 - node cluster with 30 user pods per node, Metrics Server consumes ~60MB of memory. For larger clusters, the base value matters even less, and the memory utilization will be lower, therefore this change is safe.

**Release note**:
```release-note
Reduce Metrics Server memory requirement
```