fix(ui): dark theme for code chunk in instrumentation docs (#30598)

In the "Requires Manual Instrumentation" doc, in dark mode the code chunks appear white. That's because we haven't imported our Prism theme yet.

static/app/components/events/interfaces/spans/inlineDocs.tsx

@@ -1,3 +1,5 @@
+import 'prism-sentry/index.css';
+
 import {Component} from 'react';
 import styled from '@emotion/styled';
 import * as Sentry from '@sentry/react';