fix grammar

Author: coke

xt/check-signatures.rakutest

@@ -32,7 +32,7 @@ to switch that checkout to a specific version during the test, and run
 
 I<NOTE>: This test uses introspection from the running copy of Rakudo to find
 information in the source code. If you are running a different version of raku
-then the RAKUDO_SRC directory, it may be unable to find certain method definitions.
+than the RAKUDO_SRC directory, it may be unable to find certain method definitions.
 
 To ensure that implementation details don't cause failing tests, we check only
 for certain discrepancies that are guaranteed to indicate a