CI: Remove Buildbot references

The Buildbot CI infrastructure has been fully replaced by GitHub
Actions.  Remove any lingering references from the repository.

Reviewed-by: Alexander Motin <alexander.motin@TrueNAS.com>
Signed-off-by: Brian Behlendorf <behlendorf1@llnl.gov>
Closes #17794

Author: behlendorf

.github/PULL_REQUEST_TEMPLATE.md

@@ -2,11 +2,6 @@
 
 <!--- Provide a general summary of your changes in the Title above -->
 
-<!---
-Documentation on ZFS Buildbot options can be found at
-https://openzfs.github.io/openzfs-docs/Developer%20Resources/Buildbot%20Options.html
--->
-
 ### Motivation and Context
 <!--- Why is this change required? What problem does it solve? -->
 <!--- If it fixes an open issue, please link to the issue here. -->

contrib/pyzfs/libzfs_core/test/test_libzfs_core.py

@@ -4223,7 +4223,7 @@ def reset(self):
             self.getRoot().reset()
             return
 
-        # On the Buildbot builders this may fail with "pool is busy"
+        # On the CI builders this may fail with "pool is busy"
         # Retry 5 times before raising an error
         retry = 0
         while True: