ci: drop paths-ignore from test.yml and tests-e2e.yml

These workflows are configured as required status checks in branch
protection. With paths-ignore matching the PR diff, the workflow
doesn't trigger and no status is reported — branch protection then
blocks the PR with "Expected — Waiting for status to be reported"
indefinitely. Especially common for backend-only PRs since the ignore
list included backend/**.

Run the full test suite on every PR. Cost is ~5 min per PR for
tests-linux + ~similar for tests-apple + the e2e backend smoke; small
trade for unblocking PR merges.

Workflows affected:
- tests-linux (1.26.x), tests-apple (1.26.x) in test.yml
- tests-e2e-backend (1.25.x) in tests-e2e.yml

Other workflows that still have paths-ignore (none currently in the
required-checks list) are left as-is — adding them to required later
would re-introduce the same problem.

Assisted-by: Claude:claude-opus-4-7
Signed-off-by: Ettore Di Giacinto <mudler@localai.io>