github: Upgrade download-artifact@v7 to download-artifact@v8

This has some behaviour changes, but I believe it shouldn't hit
our usage.

.github/workflows/msvcrt.yml

@@ -94,7 +94,7 @@ jobs:
           - { arch: i686, crt: msvcrt }
           - { arch: x86_64, crt: msvcrt }
     steps:
-      - uses: actions/download-artifact@v7
+      - uses: actions/download-artifact@v8
         with:
           name: linux-${{matrix.crt}}-x86_64-toolchain
       - name: Unpack cross toolchain
@@ -175,7 +175,7 @@ jobs:
           install: >-
             unzip
             make
-      - uses: actions/download-artifact@v7
+      - uses: actions/download-artifact@v8
         with:
           name: windows-${{matrix.crt}}-${{matrix.arch}}-toolchain
       - name: Unpack toolchain
@@ -200,7 +200,7 @@ jobs:
     runs-on: ubuntu-latest
     steps:
       - name: Download all artifacts
-        uses: actions/download-artifact@v7
+        uses: actions/download-artifact@v8
       - name: Rearrange files
         run: |
           rm -rf linux-asserts*