Fix css background color override for highlight box (#9314)

(cherry picked from commit 183d0e3147de1c9de6bcc58d33a6db97d920673b)

_static/css/custom.css

@@ -533,6 +533,14 @@ html.writer-html5 .rst-content dl[class]:not(.option-list):not(.field-list):not(
 html.writer-html5 .rst-content dl[class]:not(.option-list):not(.field-list):not(.footnote):not(.glossary):not(.simple) .k {
     font-style: normal;
 }
+html.writer-html5 .rst-content dl:not(.docutils) > dt, html.writer-html5 .rst-content dl[class]:not(.option-list):not(.field-list):not(.footnote):not(.citation):not(.glossary):not(.simple) > dt {
+    border-top-color: var(--highlight-background-emph-color);
+    background: var(--highlight-background-color);
+}
+html.writer-html5 .rst-content dl:not(.docutils) dl:not(.option-list):not(.field-list):not(.footnote):not(.citation):not(.glossary):not(.simple) > dt, html.writer-html5 .rst-content dl[class]:not(.option-list):not(.field-list):not(.footnote):not(.citation):not(.glossary):not(.simple) dl:not(.option-list):not(.field-list):not(.footnote):not(.citation):not(.glossary):not(.simple) > dt {
+    border-left-color: var(--highlight-background-emph-color);
+    background: var(--highlight-background-color);
+}
 html.writer-html5 .rst-content dl[class]:not(.option-list):not(.field-list):not(.footnote):not(.glossary):not(.simple) .sig-param,
 html.writer-html5 .rst-content dl[class]:not(.option-list):not(.field-list):not(.footnote):not(.glossary):not(.simple).class dt > .optional ~ em,
 html.writer-html5 .rst-content dl[class]:not(.option-list):not(.field-list):not(.footnote):not(.glossary):not(.simple).function dt > .optional ~ em,