[#117] Fix FrostFS interface usage

HTTP Gateway expects io.Reader to work with
payload, however `WithPayload` flag reads whole
payload into header object.

Signed-off-by: Alex Vanin <a.vanin@yadro.com>

internal/handler/handler.go

@@ -54,12 +54,6 @@ type PrmObjectRead struct {
 	// Address to read the object header from.
 	Address oid.Address
 
-	// Flag to read object header.
-	WithHeader bool
-
-	// Flag to read object payload. False overlaps payload range.
-	WithPayload bool
-
 	// Offset-length range of the object payload to be read.
 	PayloadRange [2]uint64
 }