doc: Use correct variable in configure_file input

In e33cc17 we removed an inner loop on the result of files(), but didn't
update the local variable to suit.

This change uses the correct iterator variable for the configure_file()
invocation.

Reported-by: Daniel Wagner <[email protected]>
Signed-off-by: Jeremy Kerr <[email protected]>

Author: jk-ozlabs

doc/meson.build

@@ -62,7 +62,7 @@ if want_docs != 'false'
     if want_docs_build
       foreach apif : api_paths
         subst = configure_file(
-            input: file,
+            input: apif,
             output: '@[email protected]',
             configuration: conf)
         c = run_command(list_man_pages, subst)