DOC/advanced tutorial "Plotting datetime charts": Minor update of code for pandas version (#3664)

Author: yvonnefroehlich

examples/tutorials/advanced/date_time_charts.py

@@ -196,7 +196,7 @@
 # uses :func:`pandas.date_range` to fill the DataArray with data, but this is not
 # essential for the creation of a valid DataArray.
 
-x = xr.DataArray(data=pd.date_range(start="2020-01-01", periods=4, freq="Q"))
+x = xr.DataArray(data=pd.date_range(start="2020-01-01", periods=4, freq="QE"))
 y = [4, 7, 5, 6]
 
 fig = pygmt.Figure()
@@ -331,7 +331,7 @@
 # found at :gmt-term:`FORMAT_CLOCK_MAP`, :gmt-term:`FORMAT_CLOCK_IN`, and
 # :gmt-term:`FORMAT_CLOCK_OUT`.
 
-x = pd.date_range("2021-04-15", periods=8, freq="6H")
+x = pd.date_range("2021-04-15", periods=8, freq="6h")
 y = [2, 5, 3, 1, 5, 7, 9, 6]
 
 fig = pygmt.Figure()