.github: doc-build: use west 0.10.0a1

Testing for the release itself.

Signed-off-by: Martí Bolívar <marti.bolivar@nordicsemi.no>
diff --git a/.github/workflows/doc-build.yml b/.github/workflows/doc-build.yml
index 2bc95e0..4d45982 100644
--- a/.github/workflows/doc-build.yml
+++ b/.github/workflows/doc-build.yml
@@ -47,7 +47,7 @@
         pip3 install setuptools wheel
         pip3 install -r scripts/requirements-base.txt
         pip3 install -r scripts/requirements-doc.txt
-        pip3 install west==0.9.0
+        pip3 install west==0.10.0a1
 
     - name: west setup
       run: |