Update SPEC.rdoc

Co-authored-by: Jeremy Evans <code@jeremyevans.net>

Author: ioquatix

SPEC.rdoc

@@ -247,7 +247,7 @@ If the Body responds to +to_ary+, it must return an +Array+ whose contents are i
 
 ==== Streaming Body
 
-The Streaming Body must respond to +call+. It must only be consumed once (calling this method consumes the body). It must not be called after being closed. It takes a +stream+ argument.
+The Streaming Body must respond to +call+, which must not be called more than once, and must not be called after being closed. The +call+ method must accept a +stream+ argument.
 
 The +stream+ argument must respond to: +read+, +write+, <tt><<</tt>, +flush+, +close+, +close_read+, +close_write+, and +closed?+. The semantics of these +IO+ methods must be a best effort match to those of a normal Ruby +IO+ or +Socket+ object, using standard arguments and raising standard exceptions. Servers may simply pass on real +IO+ objects to the Streaming Body. In some cases (e.g. when using <tt>transfer-encoding</tt> or <tt>HTTP/2+</tt>), the server may need to provide a wrapper that implements the required methods, in order to provide the correct semantics.