FIX mathematical notation in example

Author: LacombeLouis

examples/regression/1-quickstart/plot_cqr_symmetry_difference.py

@@ -111,4 +111,4 @@
 # each bound, allowing for more flexible and accurate intervals that reflect
 # the heteroscedastic nature of the data. The resulting effective coverages
 # demonstrate the theoretical guarantee of the target coverage level
-# $(1−\alpha)$.
+# :math:`1 - \alpha`.