Update rtt-target requirement in /rtic_v1/stm32l0_monotonic

Updates the requirements on [rtt-target](https://github.com/probe-rs/rtt-target) to permit the latest version.
- [Release notes](https://github.com/probe-rs/rtt-target/releases)
- [Commits](probe-rs/rtt-target@v0.3.1...v0.3.1)

---
updated-dependencies:
- dependency-name: rtt-target
  dependency-type: direct:production
...

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

Author: dependabot[bot]

rtic_v1/stm32l0_monotonic/Cargo.toml

@@ -12,7 +12,7 @@ edition = "2021"
 cortex-m-rtic = "1.0.0"
 systick-monotonic = "1.0.1"
 panic-rtt-target = { version = "0.1.2", features = ["cortex-m"] }
-rtt-target = { version = "0.3.1", features = ["cortex-m"] }
+rtt-target = { version = "0.4.0", features = ["cortex-m"] }
 stm32l0xx-hal = { version = "0.10.0", features = ["rt", "mcu-STM32L031K6Tx"] }
 
 # this lets you use `cargo fix`!