fix: issue with getAllNamedRoles function using wrong index in managementEnforcer.ts

[divyank-p]

Fix: #476

Fix the issue in getAllNamedRoles function in managementEnforcer.ts where it is supposed to element from 0-index but is using 1-index

[casbin-bot]

@nodece @Shivansh-yadav13 please review

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[hsluoyz]

@divyank-sc this PR is totally wrong. For p, alice, role-admin, the role is index-1, not index-0