Add bazel 8 to BCR presubmit (#240)

Also bump to Ubuntu 2204 since 2004 is about to EOL

.bcr/presubmit.yml

diff --git a/.bcr/presubmit.yml b/.bcr/presubmit.yml
index 3a2a60f..09ff7f7 100644
--- a/.bcr/presubmit.yml
+++ b/.bcr/presubmit.yml
@@ -1,11 +1,12 @@
 matrix:
   platform:
     - debian10
-    - ubuntu2004
+    - ubuntu2204
     - macos
     - macos_arm64
   bazel:
     - 7.x
+    - 8.x
 tasks:
   verify_targets:
     name: Verify build targets