update type to React.JSX.Element;

Author: sai6855

packages/mui-styled-engine/src/GlobalStyles/GlobalStyles.d.ts

@@ -8,4 +8,4 @@ export interface GlobalStylesProps<Theme = {}> {
 
 export default function GlobalStyles<Theme = {}>(
   props: GlobalStylesProps<Theme>,
-): React.ReactElement<unknown>;
+): React.JSX.Element;

packages/mui-system/src/cssVars/createCssVarsProvider.d.ts

@@ -88,7 +88,7 @@ export interface CreateCssVarsProviderResult<
         disableStyleSheetGeneration?: boolean;
       }
     >,
-  ) => React.ReactElement<unknown>;
+  ) => React.JSX.Element;
   useColorScheme: () => ColorSchemeContextValue<ColorScheme>;
   getInitColorSchemeScript: typeof InitColorSchemeScript;
 }