DOC: fix a typo (pandas-dev#45327)

"based or their" -> "based on their"

Author: partev

doc/source/user_guide/style.ipynb

@@ -1100,7 +1100,7 @@
     " - [.highlight_null][nullfunc]: for use with identifying missing data. \n",
     " - [.highlight_min][minfunc] and [.highlight_max][maxfunc]: for use with identifying extremeties in data.\n",
     " - [.highlight_between][betweenfunc] and [.highlight_quantile][quantilefunc]: for use with identifying classes within data.\n",
-    " - [.background_gradient][bgfunc]: a flexible method for highlighting cells based or their, or other, values on a numeric scale.\n",
+    " - [.background_gradient][bgfunc]: a flexible method for highlighting cells based on their, or other, values on a numeric scale.\n",
     " - [.text_gradient][textfunc]: similar method for highlighting text based on their, or other, values on a numeric scale.\n",
     " - [.bar][barfunc]: to display mini-charts within cell backgrounds.\n",
     " \n",