Update pattern_formatter-inl.h

Comment describing the default logging pattern is missing [%s:%#], which is the abbreviated source file + the line number.

I tried to customize our own logger by copy pasting this info, and then I noticed we had lost that information.

include/spdlog/pattern_formatter-inl.h

@@ -925,7 +925,7 @@ private:
 };
 
 // Full info formatter
-// pattern: [%Y-%m-%d %H:%M:%S.%e] [%n] [%l] %v
+// pattern: [%Y-%m-%d %H:%M:%S.%e] [%n] [%l] [%s:%#] %v
 class full_formatter final : public flag_formatter
 {
 public: