Fix typo in `Node.get_child` documentation

doc/classes/Node.xml

@@ -331,7 +331,7 @@
 			<param index="0" name="idx" type="int" />
 			<param index="1" name="include_internal" type="bool" default="false" />
 			<description>
-				Fetches a child node by its index. Each child node has an index relative its siblings (see [method get_index]). The first child is at index 0. Negative values can also be used to start from the end of the list. This method can be used in combination with [method get_child_count] to iterate over this node's children. If no child exists at the given index, this method returns [code]null[/code] and an error is generated.
+				Fetches a child node by its index. Each child node has an index relative to its siblings (see [method get_index]). The first child is at index 0. Negative values can also be used to start from the end of the list. This method can be used in combination with [method get_child_count] to iterate over this node's children. If no child exists at the given index, this method returns [code]null[/code] and an error is generated.
 				If [param include_internal] is [code]false[/code], internal children are ignored (see [method add_child]'s [code]internal[/code] parameter).
 				[codeblock]
 				# Assuming the following are children of this node, in order: