fix(ci): revert CARGO_INCREMENTAL to 0 - sccache prohibits incremental

sccache 0.7.5 errors with 'increment compilation is prohibited'
when CARGO_INCREMENTAL=1. Keep at 0 and rely on the fixed
touch-only-changed-files logic to preserve sccache cache hits.

.forgejo/workflows/botserver.yaml

@@ -16,7 +16,7 @@ jobs:
     runs-on: gbo
     env:
       RUSTC_WRAPPER: sccache
-      CARGO_INCREMENTAL: "1"
+      CARGO_INCREMENTAL: "0"
       PATH: "/home/gbuser/.cargo/bin:/usr/local/bin:/usr/local/sbin:/usr/bin:/sbin:/bin"
     steps:
       - name: Setup