build(deps): update ipykernel requirement from ~=6.14 to ~=6.15

Updates the requirements on [ipykernel]() to permit the latest version.

---
updated-dependencies:
- dependency-name: ipykernel
  dependency-type: direct:production
...

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

requirements-docs.txt

@@ -1,4 +1,4 @@
-ipykernel~=6.14
+ipykernel~=6.15
 ipython~=8.4
 Sphinx~=4.1
 sphinxcontrib-fulltoc~=1.2