inspector: removing checking of non existent field in lib/inspector.js

Seems like sessionAttached doesn't exist and no more assigned anywhere

PR-URL: nodejs#27919
Reviewed-By: Anna Henningsen <anna@addaleax.net>
Reviewed-By: Eugene Ostroukhov <eostroukhov@google.com>
Reviewed-By: Colin Ihrig <cjihrig@gmail.com>
Reviewed-By: Rich Trott <rtrott@gmail.com>
Reviewed-By: Ruben Bridgewater <ruben@bridgewater.de>

lib/inspector.js

@@ -37,12 +37,8 @@ class Session extends EventEmitter {
   connect() {
     if (this[connectionSymbol])
       throw new ERR_INSPECTOR_ALREADY_CONNECTED('The inspector session');
-    const connection =
+    this[connectionSymbol] =
       new Connection((message) => this[onMessageSymbol](message));
-    if (connection.sessionAttached) {
-      throw new ERR_INSPECTOR_ALREADY_CONNECTED('Another inspector session');
-    }
-    this[connectionSymbol] = connection;
   }
 
   [onMessageSymbol](message) {