qapi: Fix detection of doc / expression mismatch

This fixes the errors uncovered by the previous commit.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>
Message-Id: <1489582656-31133-32-git-send-email-armbru@redhat.com>
diff --git a/tests/qapi-schema/doc-missing-expr.err b/tests/qapi-schema/doc-missing-expr.err
index c0e687c..c909e26 100644
--- a/tests/qapi-schema/doc-missing-expr.err
+++ b/tests/qapi-schema/doc-missing-expr.err
@@ -1 +1 @@
-tests/qapi-schema/doc-missing-expr.json:3: Documention for 'bar' is not followed by the definition
+tests/qapi-schema/doc-missing-expr.json:3: Documentation for 'bar' is not followed by the definition