content/static/css: hide pathInput element on larger displays

"DetailsHeader-pathInput" input, used for copying package path, was
showing up on larger displays than 1080p.
This commit fixes it by using display's width (vw) instead of rem

Fixes golang/go#38162

Change-Id: Ide97e0308eb0cd56131507b933a7f3ed889ffc16
Reviewed-on: https://go-review.googlesource.com/c/pkgsite/+/238477
Reviewed-by: Julie Qiu <julie@golang.org>
diff --git a/content/static/css/stylesheet.css b/content/static/css/stylesheet.css
index eeec137..58b556a 100644
--- a/content/static/css/stylesheet.css
+++ b/content/static/css/stylesheet.css
@@ -512,7 +512,7 @@
    * copied to the clipboard. We can't use a hidden element, so
    * put this visible one very far off the screen.
    */
-  left: -62rem;
+  left: -50vw;
   position: absolute;
   top: 62rem;
 }