CI: more aggressive cache invalidation
CI: more aggressive cache invalidation

E.g. if we bump the python version, should not reuse the pip cache.
Easiest to invalidate cache if any build-specific file changes.

spesmilo/electrum,pooler/electrum-ltc,spesmilo/electrum,spesmilo/electrum,pooler/electrum-ltc,pooler/electrum-ltc,pooler/electrum-ltc,spesmilo/electrum