Update canonical_filenames.html

docs/canonical_filenames.html

@@ -69,7 +69,7 @@ <h2>Requirements</h2>
 ambiguities.  Methods employed include comparison of device and inode
 file uniqifiers, which is a fairly fast operation, or querying the OS
 for the true form of the name, which can be much slower.  Only the
-acknowledgement of the file names by the OS can validate the equality
+acknowledgment of the file names by the OS can validate the equality
 of two different cases of the same filename.</p>
 
 <p>The sixth discrepancy, illegal or insignificant characters, is especially