build: specify dotnet restore path

Author: Scoolnik

.github/workflows/dotnet_nightly.yml

@@ -32,7 +32,9 @@ jobs:
           cache-dependency-path: src/packages.lock.json
           cache: true
 
-      - run: dotnet restore --locked-mode
+      - name: Restore UE packages
+        working-directory: ./src
+        run: dotnet restore --locked-mode
 
       - name: Cache UniverseLib
         id: cache-universe-lib-build