Fix CODEOWNERS for custom-auth (#8011)

Fixes the Codeowners path for the custom-auth features

Author: tnorling

CODEOWNERS

@@ -1,7 +1,8 @@
 * @AzureAD/msal-js-public-client
 
 # MSAL Browser
-/lib/msal-browser/custom-auth @shenj @yongdiw
+/lib/msal-browser/src/custom-auth @shenj @yongdiw
+/lib/msal-browser/test/custom-auth @shenj @yongdiw
 
 # MSAL Node
 /lib/msal-node/ @AzureAD/msal-js-public-client @AzureAD/id4s-msal-team