feat: add Python 3.14 to samples testing image

Author: parthea

.kokoro/docker/Dockerfile

@@ -116,7 +116,7 @@ RUN set -ex \
   && export GNUPGHOME="$(mktemp -d)" \
   && echo "disable-ipv6" >> "${GNUPGHOME}/dirmngr.conf" \
   && /tmp/fetch_gpg_keys.sh \
-  && for PYTHON_VERSION in 2.7.18 3.7.17 3.8.20 3.9.20 3.10.15 3.11.10 3.12.7 3.13.0; do \
+  && for PYTHON_VERSION in 2.7.18 3.7.17 3.8.20 3.9.23 3.10.18 3.11.13 3.12.11 3.13.8 3.14.0; do \
   wget --no-check-certificate -O python-${PYTHON_VERSION}.tar.xz "https://www.python.org/ftp/python/${PYTHON_VERSION%%[a-z]*}/Python-$PYTHON_VERSION.tar.xz" \
   && wget --no-check-certificate -O python-${PYTHON_VERSION}.tar.xz.asc "https://www.python.org/ftp/python/${PYTHON_VERSION%%[a-z]*}/Python-$PYTHON_VERSION.tar.xz.asc" \
   && gpg --batch --verify python-${PYTHON_VERSION}.tar.xz.asc python-${PYTHON_VERSION}.tar.xz \