Update embedded-graphics requirement in /examples/twi-ssd1306

Updates the requirements on [embedded-graphics](https://github.com/embedded-graphics/embedded-graphics) to permit the latest version.
- [Release notes](https://github.com/embedded-graphics/embedded-graphics/releases)
- [Changelog](https://github.com/embedded-graphics/embedded-graphics/blob/master/CHANGELOG.md)
- [Commits](embedded-graphics/embedded-graphics@embedded-graphics-0.4.7...embedded-graphics-v0.8.1)

---
updated-dependencies:
- dependency-name: embedded-graphics
  dependency-type: direct:production
...

Signed-off-by: dependabot[bot] <support@github.com>

examples/twi-ssd1306/Cargo.toml

@@ -11,7 +11,7 @@ publish = false
 [dependencies]
 cortex-m-rt = "0.7.0"
 ssd1306 = "0.2.6"
-embedded-graphics = "0.4.7"
+embedded-graphics = "0.8.1"
 panic-semihosting = "0.6.0"
 
 [dependencies.nrf52832-hal]