plot: Fix typos in documentation of "-M" (#8444)

doc/rst/source/plot.rst

@@ -239,7 +239,7 @@ Optional Arguments
 
 .. _-M:
 
-**-M**\ [**c**\|\ **s**][**+l**\ *seclabel*][**+g**\ *fill*][**p**\ *pen*][**+r**\ *pen*][**+y**\ [*level*]] ]
+**-M**\ [**c**\|\ **s**][**+l**\ *seclabel*][**+g**\ *fill*][**p**\ *pen*][**+r**\ *pen*][**+y**\ [*level*]]
     Fill the middle area between two curves :math:`y_0(x)` and :math:`y_1(x)`, expected to be
     given via one or more pairs of separate tables, each pair of tables having the same
     number of segments (which can vary from pair to pair). Thus, the order of the even
@@ -272,9 +272,9 @@ Optional Arguments
         :width: 600 px
         :align: center
 
-        Use the |-M| option to paint the area between curves.  intersections and NaN-gaps are
+        Use the |-M| option to paint the area between curves. Intersections and NaN-gaps are
         found and the color depends on which curve is on top. Legends can be set as filled
-        rectangles or lines with colors from the fill selections via **+r**..
+        rectangles or lines with colors from the fill selections via **+r**.
 
 .. _-N: