Remove wasm32-wasip2's tier 2 status from release notes

It turns out the stars did not actually align for this to get released
in Rust 1.81 alas. Full tier 2 status for `wasm32-wasip2` required two
PRs:

* rust-lang#126967 - this made it into Rust 1.81
* rust-lang#127867 - this didn't make the cut and is in Rust 1.82 instead

This wasn't caught until just after today's release so the plan is to
remove the release notes for 1.81 and coordinate to instead add these as
release notes to 1.82.

RELEASES.md

@@ -34,7 +34,6 @@ Compiler
  - [Add Tier 3 `std` Xtensa targets:](https:/rust-lang/rust/pull/126380/) `xtensa-esp32-espidf`, `xtensa-esp32s2-espidf`, `xtensa-esp32s3-espidf`
  - [Add Tier 3 i686 Redox OS target:](https:/rust-lang/rust/pull/126192/) `i686-unknown-redox`
  - [Promote `arm64ec-pc-windows-msvc` to Tier 2.](https:/rust-lang/rust/pull/126039/)
- - [Promote `wasm32-wasip2` to Tier 2.](https:/rust-lang/rust/pull/126967/)
  - [Promote `loongarch64-unknown-linux-musl` to Tier 2 with host tools.](https:/rust-lang/rust/pull/126298/)
  - [Enable full tools and profiler for LoongArch Linux targets.](https:/rust-lang/rust/pull/127078/)
  - [Unconditionally warn on usage of `wasm32-wasi`.](https:/rust-lang/rust/pull/126662/) (see compatibility note below)