use file-consistent heading format

Author: tbrowder

doc/Language/io.pod6

@@ -155,7 +155,7 @@ the file test method C<f>:
 say "testfile".IO.f;  # OUTPUT: «True␤»
 say "lib".IO.f;       # OUTPUT: «False␤»
 
-=head1 Copying and renaming files.
+=head1 Copying and renaming files
 
 Routines C<copy>, C<rename>, and C<move> are available to avoid low-level system commands.
 See details at L<copy|/routine/copy>, L<rename|/routine/rename>, and L<move|/routine/move>.
@@ -176,6 +176,7 @@ move $fileb, '/disk2/foo';              # use move when a system rename may not
                                         # overwrites '/disk2/foo' if it exists
 move $fileb, '/disk2/foo', :createonly; # fails if '/disk2/foo' exists
 =end code
+
 =head1 Getting a directory listing
 
 To list the contents of the current directory, use the C<dir> function. It