Merge pull request #717 from rursprung/update-to-heapless-0.8

update to `heapless=0.8`

Author: burrbull

Cargo.toml

@@ -68,7 +68,7 @@ defmt-rtt = "0.4.0"
 panic-probe = { version = "0.3.0", features = [ "print-defmt" ] }
 panic-semihosting = "0.6.0"
 cortex-m-semihosting = "0.5.0"
-heapless = "0.7.16"
+heapless = "0.8"
 panic-halt = "0.2.0"
 ssd1306 = "0.7.1"
 embedded-graphics = "0.7.1"