Stop running tests workflow on main when only docs are changed

[anakin87]

Tests workflow runs for every push on main

haystack/.github/workflows/tests.yml

Lines 6 to 8 in 78e976a

	push:
	branches:
	- main

Now that docs live on the Haystack repository, this means that tests are also run when only the documents are modified, resulting in wasted computing resources.

We could find a way to run the tests only if the code is modified. This is not entirely trivial, as the push configuration on the GitHub workflow does not accept paths parameters.

[sjrl]

@anakin87 how often are we opening PRs that only modify docs?

[anakin87]

Now that PRs are automatically opened when Haystack/Core Integrations/Experimental APIs change, this is pretty common.