Update CONTRIBUTING.md

Author: emdneto

CONTRIBUTING.md

@@ -63,7 +63,7 @@ You can run `tox` with the following arguments:
 
 * `tox` to run all existing tox commands, including unit tests for all packages
   under multiple Python versions
-* `tox -e docs` to regenerate all docs 
+* `tox -e docs` to regenerate all docs
 * `tox -e py312-test-instrumentation-aiopg` to e.g. run the aiopg instrumentation unit tests under a specific
   Python version
 * `tox -e spellcheck` to run a spellcheck on all the code