Do not set request content-type for GET and HEAD request

[wuxu92]

from importer tool logic, the content-type for GET/HEAD request is used for response content, should not use it in the request.

pandora/tools/importer-rest-api-specs/components/parser/operations.go

Lines 221 to 226 in 1332cc7

	if strings.EqualFold(operation.httpMethod, "HEAD") || strings.EqualFold(operation.httpMethod, "GET") {
	if len(operation.operation.Produces) > 0 {
	contentType = operation.operation.Produces[0]
	}
	} else {
	if len(operation.operation.Consumes) > 0 {