Don't try to clean up IG name

FHIR says IG names should follow this constraint: `name.matches('[A-Z]([A-Za-z0-9_]){0,254}')`. If a user supplies an IG name with invalid characters, it will _quietly_ remove them, but it doesn't go the next step and capitalize the first letter -- so the name may still violate the constraint.

It would probably be better just to leave the name alone and warn if it violates the constraint. The current behavior is confusing to users.

See: https://chat.fhir.org/#narrow/stream/179252-IG-creation/topic/IG.20Name/near/357017209

No file or test is named in the issue. Search the TypeScript CLI code for the logic that removes invalid characters from IG names, then inspect any related tests. The behavior is done when names are left unchanged and invalid names produce a warning instead of silent cleanup, while valid names continue to satisfy the stated FHIR constraint.

Written by the indexing model from the issue text.