Remove unnecessary / at the end of CPP_CLIENT_BASE_URL

[massakam]

Motivation

CPP_CLIENT_BASE_URL ends with /, which seems unnecessary.

$ find . -type f | xargs grep --color 'CPP_CLIENT_BASE_URL'

./pkg/linux/download-cpp-client.sh:  curl -L -O ${CPP_CLIENT_BASE_URL}/deb-${PLATFORM}/apache-pulsar-client-dev.deb
./pkg/linux/download-cpp-client.sh:  curl -L -O ${CPP_CLIENT_BASE_URL}/apk-${PLATFORM}/${UNAME_ARCH}/apache-pulsar-client-dev-${CPP_CLIENT_VERSION}-r0.apk
./pkg/linux/download-cpp-client.sh:  curl -L -O ${CPP_CLIENT_BASE_URL}/rpm-${PLATFORM}/${UNAME_ARCH}/apache-pulsar-client-devel-${CPP_CLIENT_VERSION}-1.${UNAME_ARCH}.rpm
./pkg/mac/build-cpp-lib.sh:curl -O -L "$CPP_CLIENT_BASE_URL"/apache-pulsar-client-cpp-${CPP_CLIENT_VERSION}.tar.gz
./pkg/windows/download-cpp-client.bat:curl -O -L %CPP_CLIENT_BASE_URL%/%arch%-windows-static.tar.gz
./pulsar-client-cpp.txt:CPP_CLIENT_BASE_URL=https://archive.apache.org/dist/pulsar/pulsar-client-cpp-3.1.1/

Verifying this change

• Make sure that the change passes the CI checks.

Documentation

• doc-required
• doc-not-needed
• doc
• doc-complete