[contrib][postgres] Remove <> after constructor in the PG proxy code (#…

…37038)

Angle brackets are not required after constructor and, maybe, aren't
even correct, though I'm not 100% sure on what the standard says on the
matter.

It seems like clang is fine with this syntax, but when you try to build
Envoy with gcc it complains:

```
./contrib/postgres_proxy/filters/network/source/postgres_message.h: At global scope:
./contrib/postgres_proxy/filters/network/source/postgres_message.h:397:14: error: expected unqualified-id before ')' token
  397 |   Sequence<>() = default;
      |              ^
Target //contrib/exe:envoy-static failed to build
```

Given that it's at least unusual to have angle brackets after
constructor in a class template specialization let's remove them and
satisfy both gcc and clang.

It's one of the issue that prevent contrib build with gcc. It's not the
original issue reported in
#31807, but that issue is what
started the investigation.



Signed-off-by: Mikhail Krinkin <[email protected]>

contrib/postgres_proxy/filters/network/source/postgres_message.h

@@ -394,7 +394,7 @@ template <typename FirstField, typename... Remaining> class Sequence<FirstField,
 // Terminal template definition for variadic Sequence template.
 template <> class Sequence<> {
 public:
-  Sequence<>() = default;
+  Sequence() = default;
   std::string toString() const { return ""; }
   bool read(const Buffer::Instance&, uint64_t&, uint64_t&) { return true; }
   Message::ValidationResult validate(const Buffer::Instance&, const uint64_t, uint64_t&,