DOC:Fix micro-typo

Removes a extraneous µ from the docs.

Author: Yoshiki Vázquez Baeza <[email protected]>

Closes #12431 from ElDeveloper/doc-typo and squashes the following commits:

3795001 [Yoshiki Vázquez Baeza] DOC: micro-typo

Author: ElDeveloper

doc/source/visualization.rst

@@ -1652,7 +1652,7 @@ We import the rplot API:
 Examples
 ~~~~~~~~
 
-RPlot was an API for producing Trellis plots. These plots allow you toµ
+RPlot was an API for producing Trellis plots. These plots allow you to
 arrange data in a rectangular grid by values of certain attributes.
 In the example below, data from the tips data set is arranged by the attributes
 'sex' and 'smoker'. Since both of those attributes can take on one of two