docs: Fix default permission value for team block in repository_collaborators

[sinsoku]

Before the change?

• The team block's permission field documented "Defaults to pull" but the implementation uses push (Default: "push" in schema definition).
• "Must be push for personal repositories" was documented, but teams are only applicable to organization repositories.

terraform-provider-github/github/resource_github_repository_collaborators.go

Lines 52 to 62 in 256cdd8

	"team": {
	Type: schema.TypeSet,
	Optional: true,
	Description: "List of teams.",
	Elem: &schema.Resource{
	Schema: map[string]*schema.Schema{
	"permission": {
	Type: schema.TypeString,
	Optional: true,
	Default: "push",
	},

After the change?

• Updated to "Defaults to push" to match the implementation.
• Removed "Must be push for personal repositories" since teams are only applicable to organization repositories.

Pull request checklist

• [ ] Schema migrations have been created if needed (example)
• [ ] Tests for the changes have been added (for bug fixes / features)
• Docs have been reviewed and added / updated if needed (for bug fixes / features)

Does this introduce a breaking change?

Please see our docs on breaking changes to help!

• Yes
• No

[github-actions]

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