chore(administration): add SMP as code owners for the "regression/" d…

…ir tree (#21597)

* add SMP as code owners for the "regression/" dir tree

* restrict to regression/config.yaml

.github/CODEOWNERS

@@ -1,5 +1,6 @@
 * @vectordotdev/vector
 
 .github/workflows/regression.yml @vectordotdev/vector @vectordotdev/single-machine-performance
+regression/config.yaml @vectordotdev/vector @vectordotdev/single-machine-performance
 docs/ @vectordotdev/ux-team @vectordotdev/documentation
 website/ @vectordotdev/ux-team @vectordotdev/documentation