ci: remove bors configuration

.github/bors.toml

@@ -1,7 +0,0 @@
-delete_merged_branches = true
-required_approvals = 0
-use_codeowners = false
-status = [
-    "conclusion",
-]
-timeout_sec = 21600

.github/workflows/ci.yml

@@ -4,10 +4,6 @@ on:
   push:
     branches:
       - main
-      # for bors r+
-      - staging
-      # for bors try
-      - trying
   pull_request:
   merge_group:
     types: [checks_requested]