g.gui.timeline: fix typo in man page

git-svn-id: https://svn.osgeo.org/grass/grass/trunk@60036 15284696-431f-4ddb-bdfa-cd5b030d7da7

gui/wxpython/timeline/g.gui.timeline.html

@@ -3,7 +3,7 @@
 <h2>DESCRIPTION</h2>
 
 The <b>Timeline Tool</b> is a <em><a href="wxGUI.html">wxGUI</a></em> component
-which allows the user to compare the extends of temporal datasets (strds, stvds,
+which allows the user to compare the extents of temporal datasets (strds, stvds,
 str3ds) in a plot.
 <p>
 Supported features: