Fix wrong sentence in the line annotation documentation (#691)

Author: stockiNail

docs/guide/types/line.md

@@ -179,7 +179,7 @@ All of these options can be [Scriptable](../options#scriptable-options)
 
 Enabling it, you can add arrow heads at start and/or end of a line. It uses the `borderWidth` of the line options to configure the line width of the arrow head.
 
-The following options are available for can be specified per (`start` and/or `end`) arrow head, or at the top level (`arrowHeads`) which apply to all arrow heads.
+The following options can be specified per (`start` and/or `end`) arrow head, or at the top level (`arrowHeads`) which apply to all arrow heads.
 
 All of these options can be [Scriptable](../options#scriptable-options)