ci: Fix kitware apt key (#25061)

Signed-off-by: Ryan Northey <[email protected]>

Author: phlax

examples/wasm-cc/Dockerfile-envoy-build

@@ -4,6 +4,8 @@ ENV DEBIAN_FRONTEND=noninteractive
 
 RUN curl -sL https://packages.cloud.google.com/apt/doc/apt-key.gpg \
     | apt-key --keyring /usr/share/keyrings/cloud.google.gpg add - \
+    && curl -fsSL https://apt.kitware.com/keys/kitware-archive-latest.asc \
+    | apt-key add - \
     && apt-get update \
     && apt-get install --no-install-recommends -y -qq gosu \
     && groupadd -f envoygroup \