Clean up docs warnings detected by the Vale latin terms rule

Problem to solve

The Vale latin terms rule currently outputs 522 71 warnings. These should be really simple fixes, and could almost be done with a find and replace (but not quite).

Rule: https://gitlab.com/gitlab-org/gitlab/-/blob/master/doc/.vale/gitlab/LatinTerms.yml

As of Sept 27, 2021, here are the list of files that have this issue. All of these markdown files are in the /doc directory in this repo. Please feel free to open MRs for any of these issues. Thanks!

File	Line/Character	Warning
topics/autodevops/upgrading_postgresql.md	180:56	Use "for example" instead of "e.g.", but consider rewriting the sentence.
user/project/merge_requests/load_performance_testing.md	164:63	Use "for example" instead of "e.g.", but consider rewriting the sentence.
user/project/issues/csv_import.md	51:57	Use "that is" instead of "i.e.", but consider rewriting the sentence.
user/profile/account/two_factor_authentication.md	356:2	Use "for example" instead of "e.g.", but consider rewriting the sentence.