Fix broken links (#10812)

Author: LeeLenaleee

docs/samples/area/line-stacked.md

@@ -173,7 +173,7 @@ module.exports = {
 
 ## Docs
 * [Area](../../charts/area.html)
-  * [Filling modes](../../charts/area.htmll#filling-modes)
+  * [Filling modes](../../charts/area.html#filling-modes)
 * [Line](../../charts/line.html)
 * [Data structures (`labels`)](../../general/data-structures.html)
 * [Axes scales](../../axes/)

docs/samples/area/radar.md

@@ -142,7 +142,7 @@ module.exports = {
 
 ## Docs
 * [Area](../../charts/area.html)
-  * [Filling modes](../../charts/area.htmll#filling-modes)
+  * [Filling modes](../../charts/area.html#filling-modes)
   * [`propagate`](../../charts/area.html#propagate)
 * [Radar](../../charts/radar.html)
 * [Data structures (`labels`)](../../general/data-structures.html)