no strokeDasharray on markers (#2381)

* no strokeDasharray on markers

closes #2131

* always stroke-dasharray=none

* remove unused import

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Co-authored-by: Mike Bostock <mbostock@gmail.com>

Author: Fil

src/marker.js

@@ -45,6 +45,7 @@ function markerArrow(orient) {
       .attr("orient", orient)
       .attr("fill", "none")
       .attr("stroke", color)
+      .attr("stroke-dasharray", "none")
       .attr("stroke-width", 1.5)
       .attr("stroke-linecap", "round")
       .attr("stroke-linejoin", "round")
@@ -70,6 +71,7 @@ function markerCircleFill(color, context) {
     .attr("markerHeight", 6.67)
     .attr("fill", color)
     .attr("stroke", "var(--plot-background)")
+    .attr("stroke-dasharray", "none")
     .attr("stroke-width", 1.5)
     .call((marker) => marker.append("circle").attr("r", 3))
     .node();
@@ -82,6 +84,7 @@ function markerCircleStroke(color, context) {
     .attr("markerHeight", 6.67)
     .attr("fill", "var(--plot-background)")
     .attr("stroke", color)
+    .attr("stroke-dasharray", "none")
     .attr("stroke-width", 1.5)
     .call((marker) => marker.append("circle").attr("r", 3))
     .node();
@@ -95,6 +98,7 @@ function markerTick(orient) {
       .attr("markerHeight", 6)
       .attr("orient", orient)
       .attr("stroke", color)
+      .attr("stroke-dasharray", "none")
       .call((marker) => marker.append("path").attr("d", "M0,-3v6"))
       .node();
 }