v2: Gin binding tag (binding:"...") leaks a stray "form" key into the schema

swag version: v2.0.0-rc5

A struct field tagged for Gin's binding validation, e.g.:

type Example struct {
    Status string `json:"status" binding:"omitempty,oneof=a b c" form:"status"`
}

produces a schema where the property object includes a bare "form": "status" key alongside the normal type/properties. form isn't a valid OpenAPI/JSON-Schema keyword, and strict validators (e.g. kin-openapi) reject the document with something like extra sibling fields: [form].

Expected: non-OpenAPI struct tags used only for Gin binding (form, etc.) shouldn't leak into the generated schema.

Actual: they're copied through verbatim as schema sibling keys.