Update VectorCastSourcePrinter.java

Fix: render   correctly in coverage table header

Author: TimSVector

plugin/src/main/java/io/jenkins/plugins/coverage/metrics/source/VectorCastSourcePrinter.java

@@ -220,7 +220,7 @@ else if (hasMcdc && hasFc) {
             trString = tr().withClass(UNDEFINED).with(
                 td().withClass("line").with(text("Line ")),
                 td().withClass("line").with(text("St/Br")),
-                td().withClass("line").with(text(NBSP))
+                td().withClass("line").with(rawHtml(NBSP))
             ).render();
         }