docs: update Material UI version in README and remove Styled Components example

Author: OliverDudgeon

README.md

@@ -11,7 +11,7 @@ Material-UI theme for Squonk applications. Can be used independently with just M
 
 ### Material UI
 
-The colour scheme provides both a light and a dark theme. Mui v6 will automatically switch between schemes via media queries, taking into account the users system preference.
+The colour scheme provides both a light and a dark theme. Mui v7 will automatically switch between schemes via media queries, taking into account the users system preference.
 
 ```tsx
 import { CssBaseline } from '@material-ui/core';
@@ -41,14 +41,6 @@ import { ThemeProvider } from '@emotion/react';
 <ThemeProvider theme={theme}>{...}</ThemeProvider>
 ```
 
-### Styled Components
-
-```tsx
-import { ThemeProvider } from 'styled-components';
-
-<ThemeProvider theme={theme}>{...}</ThemeProvider>
-```
-
 # Release Strategy
 
 - Conventional commit messages are used to trigger new builds