Fix amount of category scales count in docs (#12139)

Author: LeeLenaleee

docs/axes/cartesian/index.md

@@ -1,6 +1,6 @@
 # Cartesian Axes
 
-Axes that follow a cartesian grid are known as 'Cartesian Axes'. Cartesian axes are used for line, bar, and bubble charts. Four cartesian axes are included in Chart.js by default.
+Axes that follow a cartesian grid are known as 'Cartesian Axes'. Cartesian axes are used for line, bar, and bubble charts. Five cartesian axes are included in Chart.js by default.
 
 * [linear](./linear.md)
 * [logarithmic](./logarithmic.md)