Bump MSRV nightly to 2022-08-25

... to enable error_in_core feature.

Author: blitz

.github/workflows/msrv_toolchain.toml

@@ -1,4 +1,4 @@
 [toolchain]
 # Oldest nightly that currently works with `cargo xtask build`.
-channel = "nightly-2022-08-08"
+channel = "nightly-2022-08-25"
 components = ["rust-src"]

README.md

@@ -108,7 +108,7 @@ prerequisites for running the tests.
 For instructions on how to create your own UEFI apps, see the [BUILDING.md](BUILDING.md) file.
 
 The uefi-rs crates currently require some [unstable features].
-The nightly MSRV is currently 2022-08-08.
+The nightly MSRV is currently 2022-08-25.
 
 [unstable features]: https://github.com/rust-osdev/uefi-rs/issues/452