Reduce code owners to CODEOWNERS and settings.yml (#24)

Previously the `CODEOWNERS` file was used to mark most code directories
with code owners. Require code owners reviews is on for settings.yml
security and at least 3 code owners need to be listed so a code owner
can make a change, get a review from another code owner and
have one code owner OOO. These settings and requirements resulted in the
inability to leverage team auto-assignment,
<https://docs.github.com/en/organizations/organizing-members-into-teams/managing-code-review-settings-for-your-team#about-auto-assignment>.
Now code owners have been limited to only the `CODEOWNERS` and
`settings.yml` files so that team auto assignment works.

.github/CODEOWNERS

@@ -1,17 +1,9 @@
-# These lines impact repository security
+# In order to utilize the [settings app](https://github.com/apps/settings) in a
+# secure manner, we must ensure that both the `CODEOWNERS` and `settings.yml`
+# file have code owners and that `settings.yml` has
+# `require_code_owner_reviews: true`.
+# We do not mark code owners for other directories as the code owners will be
+# auto-assigned first by github, preventing the use of team auto-assignment.
+# <https://docs.github.com/en/organizations/organizing-members-into-teams/managing-code-review-settings-for-your-team#about-auto-assignment>
 /.github/CODEOWNERS        @varsha888 @jcape @nick-mobilecoin
 /.github/settings.yml      @varsha888 @jcape @nick-mobilecoin
-
-# These lines prevent reviews of trivial changes blocking on particular users
-/.gitattributes
-/.gitconfig
-/.gitignore
-/.markdownlint-cli2.jsonrc
-/CHANGELOG.md
-/Cargo.toml
-/Cargo.lock
-/LICENSE
-/README.md
-/deny.toml
-/rust-toolchain.toml
-/rustfmt.toml