integer primitives are being parsed as float64

In the file req_resp_decoder.go it is obvious from the code on line [897](https://github.com/getkin/kin-openapi/blob/v0.110.0/openapi3filter/req_resp_decoder.go#L897) that the primitive being parsed is an integer and yet the code on line [898](https://github.com/getkin/kin-openapi/blob/v0.110.0/openapi3filter/req_resp_decoder.go#L898) calls `strconv.ParseFloat`