Ignore MinItems and MaxItems diff in nested block

[k-yomo]

Resolves #117

[bflad]

Hi @k-yomo 👋 Thank you so much for this fix and this appears to do what we would want here! Could you do me a favor and

• Make the same changes for tf6muxserver so the implementations are consistent in this regard
• Update the website documentation, e.g. website/docs/plugin/mux/combining-protocol-version-5-providers.mdx, under the Requirements section to something similar to "All provider schemas (except block MinItems/MaxItems`) must match"
• Create a changelog entry file, e.g. .changelog/118.txt with something similar to

```release-note:bug
tf5muxserver+tf6muxserver: Allow differing provider schema block `MinItems` and `MaxItems` as terraform-plugin-framework does not use those fields for configuration validation
```

Thanks again!

[bflad]

Looks good to me, thank you @k-yomo 🚀

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