Updated tool tip and removed min print speed disabling when slowdown for layer cooling is de-selected (#2524)

* Updated tool tip and removed min print speed disabling when slowdown for layer cooling is de-selected

* Updated tool tip to make it explicit when this setting is used.

src/libslic3r/PrintConfig.cpp

@@ -2680,7 +2680,7 @@ def = this->add("filament_loading_speed", coFloats);
 
     def = this->add("slow_down_min_speed", coFloats);
     def->label = L("Min print speed");
-    def->tooltip = L("The minimum printing speed when slow down for cooling");
+    def->tooltip = L("The minimum printing speed for the filament when slow down for better layer cooling is enabled, when printing overhangs and when feature speeds are not specified explicitly.");
     def->sidetext = L("mm/s");
     def->min = 0;
     def->mode = comAdvanced;