Update cortex-m-rt

Old versions are buggy: rust-embedded/cortex-m#469

Signed-off-by: Daniel Schaefer <[email protected]>

Author: JohnAZoidberg

Cargo.toml

@@ -5,7 +5,7 @@ version = "0.1.0"
 
 [dependencies]
 cortex-m = { version = "0.7", features = ["critical-section-single-core"]}
-cortex-m-rt = "0.7"
+cortex-m-rt = "0.7.3"
 embedded-hal = { version = "0.2.7", features = ["unproven"] }
 
 defmt = "0.3"