Fix some awkward grammar

doc/Type/Seq.pod6

@@ -13,7 +13,7 @@ generated values for later access. The same is true when assigning a Seq to an
 array.
 
 A typical use case is L<method C<lines> in C<IO::Handle>|/type/IO::Handle#method_lines>,
-which could use quite much memory if it stored all the lines read from the
+which could use a lot of memory if it stored all the lines read from the
 file. So
 
     for open('README.md').lines -> $line {