message: use markdown diff instead of two code blocks
diff: Search Modal now relies on the Search Context to access state and state setter. If you use the SidebarSearchModal as described in the [getting started documentation](https://backstage.io/docs/features/search/getting-started#using-the-search-modal), make sure to update your code with the SearchContextProvider.
  -Before:
  -
  -```tsx
  -export const Root = ({ children }: PropsWithChildren<{}>) => (
  - <SidebarPage>
  - <Sidebar>
  - <SidebarLogo />
  - <SidebarSearchModal />
  - <SidebarDivider />
  - ...
  -```
  -
  -Now:
  -
  -```tsx
  +```diff
  export const Root = ({ children }: PropsWithChildren<{}>) => (
  <SidebarPage>
  <Sidebar>
  <SidebarLogo />
  - <SearchContextProvider>
  - <SidebarSearchModal />
  - </SearchContextProvider>
  +- <SidebarSearchModal />
  ++ <SearchContextProvider>
  ++ <SidebarSearchModal />
  ++ </SearchContextProvider>
  <SidebarDivider />
  ...
  ```
  