Remove unneeded `ipykernel` tests requirement

IPython/core/tests/test_display.py

@@ -156,7 +156,6 def _get_inline_config():
     return InlineBackend.instance()
 
 
[e-mail]_without("ipykernel")
 @dec.skip_without("matplotlib")
 def test_set_matplotlib_close():
     cfg = _get_inline_config()
@@ -196,7 +195,6 def test_set_matplotlib_formats():
                 assert Figure not in f
 
 
[e-mail]_without("ipykernel")
 @dec.skip_without("matplotlib")
 def test_set_matplotlib_formats_kwargs():
     from matplotlib.figure import Figure

setup.py

@@ -185,7 +185,6 extras_require = dict(
         "curio",
         "matplotlib!=3.2.0",
         "nbformat",
-        "ipykernel",
         "numpy>=1.17",
         "pandas",
         "pygments",