Use newer nightly in check-semver (#4895)

Co-authored-by: Oliver Tale-Yazdi <oliver.tale-yazdi@parity.io>

.github/workflows/check-semver.yml

@@ -5,6 +5,8 @@ on:
     types: [opened, synchronize, reopened, ready_for_review]
     paths:
       - prdoc/*.prdoc
+env:
+  TOOLCHAIN: nightly-2024-03-01
 
 jobs:
   check-semver:
@@ -24,9 +26,9 @@ jobs:
 
       - name: Rust compilation prerequisites
         run: |
-          rustup default $(parity-publish semver --minimum-nightly-rust-version)
-          rustup target add wasm32-unknown-unknown --toolchain $(parity-publish semver --minimum-nightly-rust-version)
-          rustup component add rust-src --toolchain $(parity-publish semver --minimum-nightly-rust-version)
+          rustup default $TOOLCHAIN
+          rustup target add wasm32-unknown-unknown --toolchain $TOOLCHAIN
+          rustup component add rust-src --toolchain $TOOLCHAIN
 
       - name: extra git setup
         run: |
@@ -39,7 +41,7 @@ jobs:
           export CARGO_TARGET_DIR=target
           export RUSTFLAGS='-A warnings -A missing_docs'
           export SKIP_WASM_BUILD=1
-          if ! parity-publish --color always prdoc --since old --validate prdoc/pr_$PR.prdoc -v; then
+          if ! parity-publish --color always prdoc --since old --validate prdoc/pr_$PR.prdoc -v --toolchain $TOOLCHAIN; then
             cat <<EOF
           👋 Hello developer! The SemVer information that you declared in the prdoc file did not match what the CI detected.