build.yml: runs-on debian-aarch64 (label, not runner name)

5feab57 set runs-on to actrunner-debian-aarch64-bohr, which is the
display name of the bohr runner, not a label. Gitea Actions matches
runs-on against labels — the actual labels on bohr are debian-trixie,
aarch64, debian-aarch64. Using the runner-name as runs-on leaves the
job unrouted (no matching runner).

.gitea/workflows/build.yml

@@ -976,7 +976,7 @@ jobs:
     # __vaDriverInit_1_23, which trixie's libva 2.22 runtime cannot bind: the
     # .deb installed but vaInitialize() returned -1 on every host.  A native
     # trixie runner avoids the cross-distro ABI skew entirely.
-    runs-on: actrunner-debian-aarch64-bohr
+    runs-on: debian-aarch64
     continue-on-error: true
     steps:
       - uses: actions/checkout@v4