Rollup merge of rust-lang#101953 - GuillaumeGomez:fix-error-code-tooltip, r=notriddle

Fix tooltip display for error codes

Fixes rust-lang#101919.

You can test it [here](https://rustdoc.crud.net/imperio/fix-error-code-tooltip/index.html).

cc `@jsha`
r? `@notriddle`

Author: matthiaskrgr

src/tools/error_index_generator/error-index.css

@@ -27,10 +27,11 @@ pre .tooltip::before {
 	content: " ";
 	position: absolute;
 	top: 50%;
-	left: 16px;
+	left: 2px;
 	margin-top: -5px;
 	border-width: 5px;
 	border-style: solid;
+	height: 0px;
 }
 
 pre .tooltip:hover::before, pre .tooltip:hover::after {