Update the required approvals policy (#6783)

Based on SIG meeting discussions today: relax requirement for two
approvals from Approvers at different companies. Instead, require at
least one approver or the author to not work at the same company.

This means that if the author works at a different company than two
Approvers who have approved and work at the same company, the PR is
ready to merge.

This continues the enforcement that if an author and all Approvers
approving a PR work at the same company, additional qualified approvals
are needed.

Co-authored-by: Robert Pająk <[email protected]>

Author: MrAlias

CONTRIBUTING.md

@@ -109,10 +109,9 @@ A PR is considered **ready to merge** when:
 
   This is not enforced through automation, but needs to be validated by the
   maintainer merging.
-  * The qualified approvals need to be from [Approver]s/[Maintainer]s
-    affiliated with different companies. Two qualified approvals from
-    [Approver]s or [Maintainer]s affiliated with the same company counts as a
-    single qualified approval.
+  * At least one of the qualified approvals need to be from an
+    [Approver]/[Maintainer] affiliated with a different company than the author
+    of the PR.
   * PRs introducing changes that have already been discussed and consensus
     reached only need one qualified approval. The discussion and resolution
     needs to be linked to the PR.