[receiver/hostmetrics] Remove receiver.hostmetrics.normalizeProcessCPUUtilization feature gate

[iblancasa]

Component(s)

receiver/hostmetrics

Describe the issue you're reporting

The README.md file says:

The schedule for this feature gate is:
- Introduced in v0.97.0 (March 2024) as `alpha` - disabled by default.
- Moved to `beta` in v0.100.0 (May 2024) - enabled by default.
- Moved to `stable` in v0.102.0 (June 2024) - cannot be disabled.
- Removed three releases after `stable`.

0.107.0 was released recently so the feature gate should be removed.

[github-actions]

Pinging code owners:

• receiver/hostmetrics: @dmitryax @braydonk

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