Revision components related `model.gans.pix2pix`

[Jungwon-Lee]

What does this PR do?

Part of https://github.com/Lightning-AI/lightning-bolts/issues/839

pl_bolts.models.gans.pix2pix.components.DownSampleConv pl_bolts.models.gans.pix2pix.components.Generator pl_bolts.models.gans.pix2pix.components.PatchGAN pl_bolts.models.gans.pix2pix.components.UpSampleConv pl_bolts.models.gans.pix2pix.pix2pix_module._weights_init pl_bolts.models.gans.pix2pix.pix2pix_module.Pix2Pix

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• [x] Was this discussed/approved via a Github issue? (no need for typos and docs improvements)
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• [x] Did you make sure your PR does only one thing, instead of bundling different changes together?
• [x] Did you make sure to update the documentation with your changes?
• [x] Did you write any new necessary tests? [not needed for typos/docs]
• [x] Did you verify new and existing tests pass locally with your changes?
• [x] If you made a notable change (that affects users), did you update the CHANGELOG?

PR review

• [x] Is this pull request ready for review? (if not, please submit in draft mode)

Anyone in the community is free to review the PR once the tests have passed. If we didn't discuss your PR in Github issues there's a high chance it will not be merged.

Did you have fun?

Make sure you had fun coding 🙃

[Borda]

@Jungwon-Lee how is it going here? :rabbit: