Python: Fix typos

Author: yoff

python/ql/lib/semmle/python/security/dataflow/ReflectedXSSCustomizations.qll

@@ -59,7 +59,7 @@ module ReflectedXSS {
   class HtmlEscapingAsSanitizer extends Sanitizer {
     HtmlEscapingAsSanitizer() {
       // TODO: For now, since there is not an `isSanitizingStep` member-predicate part of a
-      // `TaintTracking::Configuration`, we use treat the output is a taint-sanitizer. This
+      // `TaintTracking::Configuration`, we treat the output as a taint-sanitizer. This
       // is slightly imprecise, which you can see in the `m_unsafe + SAFE` test-case in
       // python/ql/test/library-tests/frameworks/markupsafe/taint_test.py
       //