Bump bootloader from 0.9.19 to 0.9.20

Bumps [bootloader](https://github.com/rust-osdev/bootloader) from 0.9.19 to 0.9.20.
- [Release notes](https://github.com/rust-osdev/bootloader/releases)
- [Changelog](https://github.com/rust-osdev/bootloader/blob/v0.9.20/Changelog.md)
- [Commits](rust-osdev/bootloader@v0.9.19...v0.9.20)

---
updated-dependencies:
- dependency-name: bootloader
  dependency-type: direct:production
  update-type: version-update:semver-patch
...

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

Cargo.toml

@@ -21,7 +21,7 @@ acpi = "4.1.0"
 aml = "0.16.0"
 base64 = { version = "0.13.0", default-features = false }
 bit_field = "0.10.0"
-bootloader = { version = "0.9.19", features = ["map_physical_memory"] }
+bootloader = { version = "0.9.20", features = ["map_physical_memory"] }
 float-cmp = "0.9.0"
 hmac = { version = "0.11.0", default-features = false }
 lazy_static = { version = "1.4.0", features = ["spin_no_std"] }