move ipykernel install to be alphabetical

Author: choldgraf

setup.cfg

@@ -86,6 +86,7 @@ rtd =
     sympy
 testing =
     coverage<5.0
+    ipykernel~=5.5
     jupytext~=1.11.2
     # TODO: 3.4.0 has some warnings that need to be fixed in the tests.
     matplotlib~=3.3.0
@@ -95,7 +96,6 @@ testing =
     pytest-cov~=2.8
     pytest-regressions
     sympy
-    ipykernel~=5.5
 
 [flake8]
 max-line-length = 100