rustdoc: fix source-code-page test

Author: cynecx

src/test/rustdoc-gui/source-code-page.goml

@@ -1,6 +1,6 @@
 goto: file://|DOC_PATH|/src/test_docs/lib.rs.html
 // Check that we can click on the line number.
-click: (40, 224) // This is the position of the span for line 4.
+click: (50, 196) // This is the position of the span for line 4.
 // Unfortunately, "#4" isn't a valid query selector, so we have to go around that limitation
 // by instead getting the nth span.
 assert-attribute: (".line-numbers > span:nth-child(4)", {"class": "line-highlighted"})