Disable SEMGREP by default if no rulesets are defined

[nvuillam]

Fixes #1635

[nvuillam]

MegaLinter status: ⚠️ WARNING

Descriptor	Linter	Files	Fixed	Errors	Elapsed time
✅ BASH	bash-exec	7		0	0.02s
✅ BASH	shellcheck	7		0	0.36s
✅ BASH	shfmt	7	0	0	0.37s
✅ COPYPASTE	jscpd	yes		no	2.79s
✅ DOCKERFILE	hadolint	102		0	23.95s
✅ JSON	eslint-plugin-jsonc	20	0	0	3.67s
✅ JSON	jsonlint	18		0	5.85s
✅ JSON	v8r	20		0	13.39s
⚠️ MARKDOWN	markdownlint	279	0	4	6.03s
✅ MARKDOWN	markdown-link-check	279		0	6.04s
✅ MARKDOWN	markdown-table-formatter	279	0	0	7.66s
✅ OPENAPI	spectral	1		0	1.1s
⚠️ PYTHON	bandit	163		50	3.03s
✅ PYTHON	black	163	0	0	4.78s
✅ PYTHON	flake8	163		0	3.53s
✅ PYTHON	isort	163	0	0	0.79s
✅ PYTHON	mypy	163		0	136.62s
✅ PYTHON	pylint	163		0	20.08s
✅ REPOSITORY	git_diff	yes		no	0.34s
✅ REPOSITORY	secretlint	yes		no	12.11s
✅ REPOSITORY	trivy	yes		no	28.06s
✅ SPELL	cspell	656		0	29.36s
✅ SPELL	misspell	488	0	0	0.89s
✅ XML	xmllint	3		0	0.0s
✅ YAML	prettier	79	0	0	3.58s
✅ YAML	v8r	22		0	34.41s
✅ YAML	yamllint	80		0	1.58s

See errors details in artifact MegaLinter reports on CI Job page

[codecov-commenter]

Codecov Report

Merging #1671 (9168347) into main (59c82bd) will increase coverage by 0.01%.
The diff coverage is 88.23%.

@@            Coverage Diff             @@
##             main    #1671      +/-   ##
==========================================
+ Coverage   83.87%   83.88%   +0.01%     
==========================================
  Files         158      158              
  Lines        4112     4127      +15     
==========================================
+ Hits         3449     3462      +13     
- Misses        663      665       +2     

Impacted Files	Coverage Δ
...alinter/tests/test_megalinter/helpers/utilstest.py	88.57% <71.42%> (-0.44%)	⬇️
megalinter/MegaLinter.py	83.75% <100.00%> (ø)
megalinter/linters/SemgrepLinter.py	96.66% <100.00%> (+1.21%)	⬆️
megalinter/Linter.py	87.97% <0.00%> (-0.18%)	⬇️
megalinter/reporters/UpdatedSourcesReporter.py	91.89% <0.00%> (+2.70%)	⬆️

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