build(deps): bump heapless from 0.6.1 to 0.7.1

Bumps [heapless](https://github.com/japaric/heapless) from 0.6.1 to 0.7.1.
- [Release notes](https://github.com/japaric/heapless/releases)
- [Changelog](https://github.com/japaric/heapless/blob/master/CHANGELOG.md)
- [Commits](https://github.com/japaric/heapless/compare/v0.6.1...v0.7.1)

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

Cargo.lock

@@ -347,7 +347,6 @@ dependencies = [
  "as-slice",
  "generic-array 0.14.4",
  "hash32 0.1.1",
- "serde",
  "stable_deref_trait",
 ]
 
@@ -359,6 +358,7 @@ checksum = "c7ee8a997d259962217f40279f34201fdf06e669bafa69d7c1f4c7ff1893b5f6"
 dependencies = [
  "atomic-polyfill",
  "hash32 0.2.1",
+ "serde",
  "stable_deref_trait",
 ]
 
@@ -771,7 +771,7 @@ dependencies = [
  "cortex-m-rtic",
  "dsp",
  "embedded-hal",
- "heapless 0.6.1",
+ "heapless 0.7.1",
  "log",
  "mcp23017",
  "miniconf",

Cargo.toml

@@ -33,7 +33,7 @@ cortex-m-rt = { version = "0.6", features = ["device"] }
 log = { version = "0.4", features = ["max_level_trace", "release_max_level_info"] }
 rtt-target = { version = "0.3", features = ["cortex-m"] }
 serde = { version = "1.0", features = ["derive"], default-features = false }
-heapless = { version = "0.6", features = ["serde"] }
+heapless = { version = "0.7", features = ["serde"] }
 cortex-m-rtic = "0.5.6"
 embedded-hal = "0.2.5"
 nb = "1.0.0"