Backport PR #48444 on branch 1.5.x (CI: Pin ipython version) (#48449)

Backport PR #48444: CI: Pin ipython version

Co-authored-by: Patrick Hoefler <[email protected]>

Author: meeseeksmachine

doc/source/user_guide/timeseries.rst

@@ -1981,7 +1981,6 @@ frequency. Arithmetic is not allowed between ``Period`` with different ``freq``
    p = pd.Period("2012-01", freq="2M")
    p + 2
    p - 1
-   @okexcept
    p == pd.Period("2012-01", freq="3M")