Update SPEC.rdoc

Author: ioquatix

SPEC.rdoc

@@ -207,7 +207,7 @@ The headers must be an unfrozen +Hash+. The header keys must be +String+ values.
 * The headers must not contain a <tt>"status"</tt> key.
 * Header keys must conform to {RFC7230}[https://tools.ietf.org/html/rfc7230] token specification, i.e. cannot contain non-printable <tt>ASCII</tt>, <tt>DQUOTE</tt> or <tt>(),/:;<=>?@[\]{}</tt>.
 * Header keys must not contain uppercase <tt>ASCII</tt> characters (A-Z).
-* Header values must be either a +String+, or an +Array+ of +String+ values, such that each +String+ must not contain characters with an <tt>ASCII</tt> ordinal below <tt>040</tt> (32).
+* Header values must be either a +String+, or an +Array+ of +String+ values, such that each +String+ must not contain characters with an ASCII ordinal below 040 (32).
 
 ==== The <tt>content-type</tt> Header