content/static/css: remove commented line to enable executable examples

This change replaces display: none; with display: flex; to enable
executable examples in in the documentation page. The HTML changes used
for this CSS change requires the executable-examples feature flag.

Updates golang/go#36865

Change-Id: I2cb62438663ecbfbccfe1f5b4b6b1e2dbe3e3916
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/253599
Reviewed-by: Julie Qiu <[email protected]>

Author: Miguel Acero

content/static/css/stylesheet.css

@@ -1252,8 +1252,7 @@ code {
 }
 .Documentation-exampleButtonsContainer {
   align-items: center;
-  /* This will change back to display: flex; when we enable playground buttons */
-  display: none;
+  display: flex;
   justify-content: flex-end;
   margin-top: 0.5rem;
 }