Make use of backtick consistent

Author: cvanelteren

ultraplot/axes/base.py

@@ -317,7 +317,7 @@
     The axes title. Can optionally be a sequence strings, in which case
     the title will be selected from the sequence according to `~Axes.number`.
 abc : bool or str or sequence, default: :rc:`abc`
-    The "a-b-c" subplot label style. Must contain the character `a` or ``A``,
+    The "a-b-c" subplot label style. Must contain the character `a` or `A`,
     for example ``'a.'``, or ``'A'``. If ``True`` then the default style of
     ``'a'`` is used. The `a` or ``A`` is replaced with the alphabetic character
     matching the `~Axes.number`. If `~Axes.number` is greater than 26, the