Update MSRV from 1.76 to 1.77 (#5322)

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I am preparing a separate PR that adds support for JXL with `jxl-oxide`,
which is unlikely to be added to the `image` crate anytime soon (more
context will be provided in that PR).

`jxl-oxide` makes use of the
[`array::each_mut`](https://doc.rust-lang.org/stable/std/primitive.array.html#method.each_mut)
API which was stabilized in 1.77, which is the motivation for this MSRV
bump.

Rust 1.77 was officially released to stable on 21 March, 2024.

scripts/check.sh

@@ -9,7 +9,7 @@ set -x
 # Checks all tests, lints etc.
 # Basically does what the CI does.
 
-cargo +1.76.0 install --quiet typos-cli
+cargo +1.77.0 install --quiet typos-cli
 
 export RUSTFLAGS="-D warnings"
 export RUSTDOCFLAGS="-D warnings" # https://github.com/emilk/egui/pull/1454

scripts/clippy_wasm/clippy.toml

@@ -6,7 +6,7 @@
 # -----------------------------------------------------------------------------
 # Section identical to the root clippy.toml:
 
-msrv = "1.76"
+msrv = "1.77"
 
 allow-unwrap-in-tests = true