CODEOWNERS: remove @braydonk and @jefferbrecht

Going forward, @JeffLuoo will be the primary owner for the
`out_stackdriver` plugin. I am removing myself an @jefferbrecht from any
code owner status. Jeff Luo is now fully in charge of the plugin, along
with anyone he may want to add as code owners in the future.

I do still have maintainer privileges on this repo, which was simply so
I could merge PRs that only touched the `out_stackdriver` plugin/test
code without needing to bother maintainers. I can't do it myself, but I
would suggest this permission and general interaction be passed on to
@JeffLuoo as well.

Signed-off-by: braydonk <braydonk@google.com>

Author: braydonk

CODEOWNERS

@@ -63,7 +63,7 @@
 /plugins/out_datadog     @nokute78 @edsiper
 /plugins/out_es          @pettitwesley @edsiper
 /plugins/out_pgsql       @sxd
-/plugins/out_stackdriver @braydonk @jefferbrecht @jeffluoo
+/plugins/out_stackdriver @jeffluoo
 
 # AWS Plugins
 /plugins/out_s3               @fluent/aws-fluent-bit-maintainers
@@ -85,8 +85,8 @@
 
 # Google test code
 # --------------
-/tests/runtime/out_stackdriver.c @braydonk @jefferbrecht @jeffluoo
-/tests/runtime/data/stackdriver  @braydonk @jefferbrecht @jeffluoo
+/tests/runtime/out_stackdriver.c @jeffluoo
+/tests/runtime/data/stackdriver  @jeffluoo
 
 # Devcontainer
 /.devcontainer                  @patrick-stephens @niedbalski @edsiper