Bump Rust to version 1.77

When trying to build rowan we get this error

    error: package `rowan v0.15.16` cannot be built because
    it requires rustc 1.77.0 or newer, while the currently active rustc
    version is 1.75.0

So let's upgrade to 1.77 to allow us to build rowan.

Cargo.toml

@@ -13,7 +13,7 @@ version = "0.1.0"
 [workspace.package]
 # This must be kept in sync with rust-toolchain.toml; please see that file for
 # more information.
-rust-version = "1.75"
+rust-version = "1.77"
 
 [features]
 rust_embedded = [

rust-toolchain.toml

@@ -5,9 +5,11 @@
 # you'd like to use. When you do so, update this to the first Rust version that
 # includes that feature. Whenever this value is updated, the rust-version field
 # in Cargo.toml must be updated as well.
-channel = "1.75"
+channel = "1.77"
 components = ["clippy", "rustfmt"]
-targets = ["thumbv6m-none-eabi",
-           "thumbv7em-none-eabi",
-           "riscv32imac-unknown-none-elf",
-           "riscv32imc-unknown-none-elf"]
+targets = [
+    "thumbv6m-none-eabi",
+    "thumbv7em-none-eabi",
+    "riscv32imac-unknown-none-elf",
+    "riscv32imc-unknown-none-elf",
+]