fix typo

Co-authored-by: Arthur Baars <aibaars@github.com>

Author: erik-krogh

ql/ql/src/codeql_ql/ast/internal/AstMocks.qll

@@ -66,7 +66,7 @@ module MockModule {
     bindingset[this]
     Range() { this = this }
 
-    /** Gets tthe name of this mocked module. */
+    /** Gets the name of this mocked module. */
     abstract string getName();
 
     /** Gets the id for the `i`th mocked member of this module. */