prevent occasional The Cypress App could not be downloaded error from making CI fail on unrelated jobs

[adrienjoly]

cf logs of "Functional tests" CI job, not relying on Cypress:

$ npm ci --prefer-offline --no-audit
npm WARN deprecated string-similarity@[4](https://github.com/openwhyd/openwhyd/actions/runs/5941074269/job/16111085627#step:4:4).0.4: Package no longer supported. Contact Support at https://www.npmjs.com/support for more info.
npm WARN deprecated w3c-hr-time@1.0.2: Use your platform's native performance.now() and performance.timeOrigin.
npm WARN deprecated uuid@3.3.3: Please upgrade  to version 7 or higher.  Older versions may use Math.random() in certain circumstances, which is known to be problematic.  See https://v8.dev/blog/math-random for details.
npm WARN deprecated natives@1.1.6: This module relies on Node.js's internals and will break at some point. Do not use it, and update to graceful-fs@4.x.
npm WARN deprecated request@2.88.2: request has been deprecated, see https://github.com/request/request/issues/3142
npm WARN deprecated har-validator@[5](https://github.com/openwhyd/openwhyd/actions/runs/5941074269/job/16111085627#step:4:5).1.3: this library is no longer supported
npm WARN deprecated mkdirp@0.3.0: Legacy versions of mkdirp are no longer supported. Please update to mkdirp 1.x. (Note that the API surface has changed to use Promises in 1.x.)
npm ERR! code 1
npm ERR! path /home/runner/work/openwhyd/openwhyd/node_modules/cypress
npm ERR! command failed
npm ERR! command sh -c node index.js --exec install
npm ERR! Installing Cypress (version: 12.17.4)
npm ERR! 
npm ERR! [STARTED] Task without title.
npm ERR! The Cypress App could not be downloaded.
npm ERR! 
npm ERR! Does your workplace require a proxy to be used to access the Internet? If so, you must configure the HTTP_PROXY environment variable before downloading Cypress. Read more: https://on.cypress.io/proxy-configuration
npm ERR! 
npm ERR! Otherwise, please check network connectivity and try again:
npm ERR! 
npm ERR! ----------
npm ERR! 
npm ERR! URL: https://download.cypress.io/desktop/12.17.4?platform=linux&arch=x[6](https://github.com/openwhyd/openwhyd/actions/runs/5941074269/job/16111085627#step:4:6)4
npm ERR! Error: Failed downloading the Cypress binary.
npm ERR! Response code: 502
npm ERR! Response message: Bad Gateway
npm ERR! 
npm ERR! ----------
npm ERR! 
npm ERR! Platform: linux-x64 (Ubuntu - 20.04)
npm ERR! Cypress Version: 12.1[7](https://github.com/openwhyd/openwhyd/actions/runs/5941074269/job/16111085627#step:4:8).4
npm ERR! [FAILED] The Cypress App could not be downloaded.
npm ERR! [FAILED] 
npm ERR! [FAILED] Does your workplace require a proxy to be used to access the Internet? If so, you must configure the HTTP_PROXY environment variable before downloading Cypress. Read more: https://on.cypress.io/proxy-configuration
npm ERR! [FAILED] 
npm ERR! [FAILED] Otherwise, please check network connectivity and try again:
npm ERR! [FAILED] 
npm ERR! [FAILED] ----------
npm ERR! [FAILED] 
npm ERR! [FAILED] URL: https://download.cypress.io/desktop/12.17.4?platform=linux&arch=x64
npm ERR! [FAILED] Error: Failed downloading the Cypress binary.
npm ERR! [FAILED] Response code: 502
npm ERR! [FAILED] Response message: Bad Gateway
npm ERR! [FAILED] 
npm ERR! [FAILED] ----------
npm ERR! [FAILED] 
npm ERR! [FAILED] Platform: linux-x64 (Ubuntu - 20.04)
npm ERR! [FAILED] Cypress Version: 12.17.4

npm ERR! A complete log of this run can be found in: /home/runner/.npm/_logs/2023-0[8](https://github.com/openwhyd/openwhyd/actions/runs/5941074269/job/16111085627#step:4:9)-22T[15](https://github.com/openwhyd/openwhyd/actions/runs/5941074269/job/16111085627#step:4:16)_45_30_[28](https://github.com/openwhyd/openwhyd/actions/runs/5941074269/job/16111085627#step:4:29)6Z-debug-0.log
Error: Process completed with exit code 1.