DOC: Remove simple_legend examples from User Demo

The same plots are contained in the legend guide at
https://matplotlib.org/devdocs/users/explain/axes/legend_guide.html#legend-location
https://matplotlib.org/devdocs/users/explain/axes/legend_guide.html#multiple-legends-on-the-same-axes

And there, they aleady have accompanying descriptions. Instead of moving
 these examples to the text_labels_and_annotations section, I've decided
  to remove them and instead link the existing legend examples with a
  see also to the legend guide. I believe this is more helpful than
  having more uncommented legend examples.

Author: timhoffm

galleries/examples/text_labels_and_annotations/figlegend_demo.py

@@ -25,3 +25,9 @@
 # %%
 # The outside positioning is discussed in detail here:
 # https://matplotlib.org/stable/users/explain/axes/legend_guide.html#figure-legends
+#
+#
+# .. seealso::
+#
+#    The :ref:`legend_guide` contains an in depth discussion on the configuration
+#    options for legends.

galleries/examples/text_labels_and_annotations/legend.py

@@ -37,3 +37,8 @@
 #
 #    - `matplotlib.axes.Axes.plot` / `matplotlib.pyplot.plot`
 #    - `matplotlib.axes.Axes.legend` / `matplotlib.pyplot.legend`
+#
+# .. seealso::
+#
+#    The :ref:`legend_guide` contains an in depth discussion on the configuration
+#    options for legends.

galleries/examples/text_labels_and_annotations/legend_demo.py

@@ -178,3 +178,10 @@ def create_artists(self, legend, orig_handle,
           handlelength=2.5, handleheight=3)
 
 plt.show()
+
+# %%
+#
+# .. seealso::
+#
+#    The :ref:`legend_guide` contains an in depth discussion on the configuration
+#    options for legends.