Insurance — Personal injury protection — Demand letter — Demand letters that listed total amounts billed but failed to provide exact amount for which insurer will be sued if it does not pay claims did not satisfy requirements of section 627.736(10) — Language in letters instructing insurer that it should advise provider if total amounts due are different than that noted in demand letters does not establish waiver of condition precedent or shift to insurer the provider’s statutory burden of putting insurer on notice of actual amount that provider is seeking