docs: fix typo in rules.py (#2636)

### Description

Simple typo fix in `rules.py`

### QC
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* [x] The PR contains a test case for the changes or the changes are
already covered by an existing test case.
* [x] The documentation (`docs/`) is updated to reflect the changes or
this is not necessary (e.g. if the change does neither modify the
language nor the behavior or functionalities of Snakemake).

snakemake/linting/rules.py

@@ -115,7 +115,7 @@ def lint_missing_software_definition(self, rule):
                     body="While environment modules allow to document and deploy the required software on a certain "
                     "platform, they lock your workflow in there, disabling easy reproducibility on other machines "
                     "that don't have exactly the same environment modules. Hence env modules (which might be beneficial "
-                    "in certain cluster environments), should allways be complemented with equivalent conda "
+                    "in certain cluster environments), should always be complemented with equivalent conda "
                     "environments.",
                     links=[links.package_management, links.containers],
                 )