Fix typos and grammar - #715

Running Vale across on the following files affected by this PR:

- configuration/auth/custom.mdx
- handling-writes/handling-update-conflicts.mdx
- integrations/flutterflow/attachments.mdx
- maintenance-ops/monitoring-and-alerting.mdx
- resources/faq.mdx
- resources/local-first-software.mdx
- resources/supported-platforms.mdx

Attempting to initialize Vale linter...
Customer vale configuration detected. Attempting to sync packages...
Packages synced successfully.
Attempting to run Vale spellcheck...
Vale spellcheck completed successfully.

handling-writes/handling-update-conflicts.mdx:
	- 6:24    Did you really mean 'unopinionated'?

maintenance-ops/monitoring-and-alerting.mdx:
	- 172:114    Did you really mean 'triaging'?

resources/faq.mdx:
	- 8:261    Did you really mean 'datastore'?

resources/supported-platforms.mdx:
	- 15:39     Did you really mean 'Sonoma'?
	- 17:33     Did you really mean 'glibc'?
	- 87:17     Did you really mean 'glibc'?
	- 100:67    Did you really mean 'glibc'?
	- 173:45    Use 'Postgres' instead of 'PostgreSQL'.


Found 8 suggested changes across 4 files in 1268.80ms