fix: unnecessary trailing line break for read-only source code (#2033)

* fix: trim

* fix: 兼容LiveDemo情况

---------

Co-authored-by: Peach <scdzwyxst@gmail.com>

src/client/theme-default/builtins/SourceCode/index.tsx

@@ -49,7 +49,7 @@ const SourceCode: FC<SourceCodeProps> = (props) => {
   const code = (
     <Highlight
       {...defaultProps}
-      code={children}
+      code={props.textarea ? children : children.trim()}
       language={SIMILAR_DSL[lang] || lang}
       theme={undefined}
     >