docs(contributing): refactor `pre-commit` instructions

[SauravMaheshkar]

At the moment, the pre-commit instructions aren't linked from anywhere. This PR updates the contributing guide by linking the pre-commit instructions.

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 81.82%. Comparing base (c802af8) to head (a3835bc).

Additional details and impacted files

```diff @@ Coverage Diff @@ ## master #1582 +/- ## ======================================= Coverage 81.82% 81.82% ======================================= Files 145 145 Lines 6140 6140 ======================================= Hits 5024 5024 Misses 1116 1116 ```

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[guarin]

I also saw that PRECOMMITHOOKS.md still refers to requirements/dev.txt which doesn't exist anymore. Could you update that part as well?

[SauravMaheshkar]

I also saw that PRECOMMITHOOKS.md still refers to requirements/dev.txt which doesn't exist anymore. Could you update that part as well?

Addressed in ebdb09f