Remove unused imports. Explicitly import a few deep imports.

gui/qt/invoice_list.py

@@ -23,11 +23,10 @@
 # CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
 # SOFTWARE.
 
-
 from .util import *
 from electrum.i18n import _
-from electrum.util import block_explorer_URL, format_satoshis, format_time
-from electrum.plugins import run_hook
+from electrum.util import format_time
+
 
 class InvoiceList(MyTreeWidget):
     filter_columns = [0, 1, 2, 3]  # Date, Requestor, Description, Amount