jenkins.sh: remove spurious 'npm install'
jenkins.sh: remove spurious 'npm install'

Just let npm install matrix-js-sdk, rather than installing the one from jenkins

aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk,matrix-org/matrix-react-sdk,aperezdc/matrix-react-sdk,matrix-org/matrix-react-sdk