Bump urllib3 from 1.26.16 to 1.26.18 in /python

Bumps [urllib3](https://github.com/urllib3/urllib3) from 1.26.16 to 1.26.18.
- [Release notes](https://github.com/urllib3/urllib3/releases)
- [Changelog](https://github.com/urllib3/urllib3/blob/main/CHANGES.rst)
- [Commits](urllib3/urllib3@1.26.16...1.26.18)

---
updated-dependencies:
- dependency-name: urllib3
  dependency-type: indirect
...

Signed-off-by: dependabot[bot] <support@github.com>

python/examples/requirements.txt

@@ -7,7 +7,7 @@
 absl-py==1.4.0 \
     --hash=sha256:0d3fe606adfa4f7db64792dd4c7aee4ee0c38ab75dfd353b7a83ed3e957fcb47 \
     --hash=sha256:d2c244d01048ba476e7c080bd2c6df5e141d211de80223460d5b3b8a2a58433d
-    # via -r requirements.in
+    # via -r examples/requirements.in
 cachetools==5.3.1 \
     --hash=sha256:95ef631eeaea14ba2e36f06437f36463aac3a096799e876ee55e5cdccb102590 \
     --hash=sha256:dce83f2d9b4e1f732a8cd44af8e8fab2dbe46201467fc98b3ef8f269092bf62b
@@ -113,7 +113,7 @@ google-cloud-core==2.3.3 \
 google-cloud-storage==2.10.0 \
     --hash=sha256:934b31ead5f3994e5360f9ff5750982c5b6b11604dc072bc452c25965e076dc7 \
     --hash=sha256:9433cf28801671de1c80434238fb1e7e4a1ba3087470e90f70c928ea77c2b9d7
-    # via -r requirements.in
+    # via -r examples/requirements.in
 google-crc32c==1.5.0 \
     --hash=sha256:024894d9d3cfbc5943f8f230e23950cd4906b2fe004c72e29b209420a1e6b05a \
     --hash=sha256:02c65b9817512edc6a4ae7c7e987fea799d2e0ee40c53ec573a692bee24de876 \