Fix repeated words

Author: rbuj

help/C/superscript.page

@@ -19,7 +19,7 @@
     </p>
     </example>
     <p>
-    To enter superscript numbers with the mouse select the number mode using the the <gui>↑n</gui> and <gui>↓n</gui> buttons.
+    To enter superscript numbers with the mouse select the number mode using the <gui>↑n</gui> and <gui>↓n</gui> buttons.
     When one of these modes is active clicking the number buttons will enter numbers in superscript or subscript.
     To return to normal number mode click the active button.
     </p>