chore: bump urllib3 from 1.26.12 to 1.26.18 (#496)

Source-Link: googleapis/synthtool@febaccc
Post-Processor: gcr.io/cloud-devrel-public-resources/owlbot-python:latest@sha256:caffe0a9277daeccc4d1de5c9b55ebba0901b57c2f713ec9c876b0d4ec064f61

Co-authored-by: Owl Bot <gcf-owl-bot[bot]@users.noreply.github.com>

Author: gcf-owl-bot[bot]

.github/.OwlBot.lock.yaml

@@ -13,5 +13,5 @@
 # limitations under the License.
 docker:
   image: gcr.io/cloud-devrel-public-resources/owlbot-python:latest
-  digest: sha256:30470597773378105e239b59fce8eb27cc97375580d592699206d17d117143d0
-# created: 2023-11-03T00:57:07.335914631Z
+  digest: sha256:caffe0a9277daeccc4d1de5c9b55ebba0901b57c2f713ec9c876b0d4ec064f61
+# created: 2023-11-08T19:46:45.022803742Z