fix(init): allow for spec on scope-only arg

[wraithgar]

Closes #5175

[npm-cli-bot]

no statistically significant performance changes detected

timing results

app-large	clean	lock-only	cache-only	cache-only peer-deps	modules-only	no-lock	no-cache	no-modules	no-clean	no-clean audit
npm@8	44.938 ±2.93	21.738 ±0.62	19.226 ±0.00	23.176 ±1.80	3.252 ±0.02	3.238 ±0.03	2.670 ±0.07	13.477 ±0.01	2.600 ±0.03	3.835 ±0.10
#5206	41.595 ±1.00	21.460 ±0.22	19.642 ±0.16	22.115 ±0.25	3.256 ±0.00	3.250 ±0.02	2.703 ±0.13	13.684 ±0.04	2.633 ±0.01	3.895 ±0.05

app-medium	clean	lock-only	cache-only	cache-only peer-deps	modules-only	no-lock	no-cache	no-modules	no-clean	no-clean audit
npm@8	34.694 ±4.55	15.975 ±0.13	14.376 ±0.10	15.129 ±0.17	3.015 ±0.03	3.040 ±0.03	2.686 ±0.02	9.731 ±0.08	2.514 ±0.00	3.505 ±0.12
#5206	30.460 ±0.22	16.252 ±0.10	14.299 ±0.00	15.675 ±0.82	2.988 ±0.04	2.973 ±0.03	2.720 ±0.06	9.619 ±0.01	2.532 ±0.00	3.537 ±0.14