docs: Fix typos and file naming inconsistencies in provider documentation (#63683)

* fix typos in documentation_building.rst

* fix typo by renaming the pagerduty.rst file

pagerduty.rst file was named as pagerdurty in providers/pagerduty/docs/connections/ path.
This commit is to rename it to the consistent naming.

* fix double include:: for INSTALLING_PROVIDERS_FROM_SOURCES_CONTENT_RST in check_provider_docs.py

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Co-authored-by: Jarek Potiuk <jarek@potiuk.com>