Upgrade terraform-provider-github to v5.26.0

[pulumi-bot]

This PR was generated via $ upgrade-provider pulumi/pulumi-github --kind=all.

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• Upgrading terraform-provider-github from 5.25.1 to 5.26.0.
  Fixes Upgrade terraform-provider-github to v5.26.0 #366
• Upgrading pulumi-terraform-bridge from v3.47.2 to v3.48.0.

[github-actions]

Does the PR have any schema changes?

Found 2 breaking changes:
Resource "github:index/actionsRunnerGroup:ActionsRunnerGroup" property "allowsPublicRepositories" is no longer Required
Type "github:index/RepositoryPages:RepositoryPages" property "source" is no longer Required

New functions:

• index/getRepositoryAutolinkReferences.getRepositoryAutolinkReferences
• index/getRepositoryEnvironments.getRepositoryEnvironments
• index/getRestApi.getRestApi

Maintainer note: consult the runbook for dealing with any breaking changes.