fix version switcher CSS (ray-project#54730)

Signed-off-by: dshepelev15 <[email protected]>

Author: cristianjd

doc/source/_static/css/custom.css

@@ -394,6 +394,12 @@ table.autosummary tr > td:first-child > p > a > code > span {
   overflow-y: scroll;
 }
 
+/* Right align the version switcher dropdown menu to prevent it from going off screen */
+.version-switcher__menu[data-bs-popper] {
+  right: 0;
+  left: unset;
+}
+
 /* Hide the RTD version switcher since we are using PyData theme one */
 readthedocs-flyout {
   display: none !important;