src: fix build on CentOS

85af1a6 was added (squashed into another commit) without running
through CI. Unfortunately, it breaks some of the CI builds, notably on
three of the CentOS setups.

Undoing that one small change to get builds green again.

Refs: nodejs#7547 (comment)
PR-URL: nodejs#7873
Reviewed-By: Jeremiah Senkpiel <fishrock123@rocketmail.com>
Reviewed-By: Johan Bergström <bugs@bergstroem.nu>
Reviewed-By: Ben Noordhuis <info@bnoordhuis.nl>
Reviewed-By: Anna Henningsen <anna@addaleax.net>

src/connection_wrap.h

@@ -23,7 +23,8 @@ class ConnectionWrap : public StreamWrap {
                  v8::Local<v8::Object> object,
                  ProviderType provider,
                  AsyncWrap* parent);
-  ~ConnectionWrap() = default;
+  ~ConnectionWrap() {
+  }
 
   UVType handle_;
 };