Improve error message presented when computeclass creation fails because of memory being present in resources/limits.

[sangee2004]

acorn version v0.10.0-rc2-9-g43dbcbf4+43dbcbf4

Steps to reproduce the problem:

1. Try to create computeclass with memory present in resources/limits

   kind: ClusterComputeClass
   apiVersion: admin.acorn.io/v1
   default: false
   metadata:
   name: cc-res-inv
   description: Large compute for linux on arm64
   cpuScaler: 0.75
   supportedRegions:
   - local
   memory:
   default: 20M
   min: 10M
   max: 100M
   resources:
   limits:
   memory: 50M
   gpu-vendor.example/example-gpu: 2
   requests:
   gpu-vendor.example/example-gpu: 2

2. This fails as expected with following error message:

   The ClusterComputeClass "cc-res-inv" is invalid: spec.resources.limits.memory: Invalid value: resource.Quantity{i:resource.int64Amount{value:50, scale:6}, d:resource.infDecAmount{Dec:(*inf.Dec)(nil)}, s:"50M", Format:"DecimalSI"}: Cannot specifiy spec.resources.limits.memory. Use explicit spec.cpuScaler and spec.memory instead

Expected Behavior: Error message can be improved to be more readable in this case.