[Net] Change HTTPRequest timeout type to double.

For consistency with the Timer class and general time representation
inside the engine.

scene/main/http_request.h

@@ -96,7 +96,7 @@ private:
 
 	int max_redirects = 8;
 
-	int timeout = 0;
+	double timeout = 0;
 
 	void _redirect_request(const String &p_new_url);
 
@@ -146,8 +146,8 @@ public:
 
 	Timer *timer;
 
-	void set_timeout(int p_timeout);
-	int get_timeout();
+	void set_timeout(double p_timeout);
+	double get_timeout();
 
 	void _timeout();