refactor: Enable more clang-tidy readability checks (#6595)

Co-authored-by: Sergey Kuznetsov <kuzzz99@gmail.com>

src/test/protocol/SeqProxy_test.cpp

@@ -42,7 +42,7 @@ struct SeqProxy_test : public beast::unit_test::suite
     }
 
     // Verify streaming.
-    bool
+    static bool
     streamTest(SeqProxy seqProx)
     {
         std::string const type{seqProx.isSeq() ? "sequence" : "ticket"};