Bump actions/upload-artifact from v3 to v4.4.0 (#1973)

and actions/download-artifact from v3 to v4.1.8

Author: t-sommer

.github/workflows/build-spec.yml

@@ -37,7 +37,7 @@ jobs:
         PowerShell -ExecutionPolicy Bypass -Command ./generate_figures.ps1
 
     - name: Create ZIP archive
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4.4.0
       with:
         name: schema-figures
         path: docs/images/schema/*.png
@@ -53,7 +53,7 @@ jobs:
       with:
         submodules: recursive
 
-    - uses: actions/download-artifact@v3
+    - uses: actions/download-artifact@v4.1.8
       with:
         name: schema-figures
         path: docs/images/schema
@@ -88,7 +88,7 @@ jobs:
         cp docs/images/schema/*.png build/images/schema
 
     - name: Create ZIP archive
-      uses: actions/upload-artifact@v3
+      uses: actions/upload-artifact@v4.4.0
       with:
         name: FMI-Specification
         path: build/*