build: reenable gitleaks

[goncalo-frade-iohk]

It seems .gitleaksignore is experimental and doesn't work so well, so we are going to use the common way that is comment //gitleaks:allow. We could also try to use .gitconfig.toml file to apply rules for test but this comment seems more appropriate.

[atala-dev]

🦙 MegaLinter status: ⚠️ WARNING

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ ACTION	actionlint	1		0	0.08s
✅ EDITORCONFIG	editorconfig-checker	2		0	0.04s
⚠️ REPOSITORY	devskim	yes		6	1.01s
✅ REPOSITORY	dustilock	yes		no	0.05s
✅ REPOSITORY	gitleaks	yes		no	1.48s
✅ REPOSITORY	git_diff	yes		no	0.02s
✅ REPOSITORY	secretlint	yes		no	4.17s
✅ REPOSITORY	syft	yes		no	0.46s
✅ REPOSITORY	trivy	yes		no	6.05s
✅ YAML	prettier	1		0	0.49s
✅ YAML	v8r	1		0	2.82s
✅ YAML	yamllint	1		0	0.27s

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[hamada147]

Unfortunately you will have to add the comment on every line that has the gitleaks

[hamada147]

LGTM