Clear UV Pins

Removes the Pin property from all points of the object, without having to select anything first. Afterward, all UV elements can be moved freely again. If you want to unlock only certain elements, you can manually select the corresponding UV points, edges, or polygons and then execute the Remove UV Pins command.

To temporarily disable the locking of UV elements, you can also turn off the Use UV Pins option.
You'll find this option as an icon above the UV Editor in the UVEdit layout (see figure below).