Add nand4 leakage to sky130 tech

Author: mguthaus

technology/sky130/tech/tech.py

@@ -748,6 +748,7 @@
 spice["inv_leakage"] = 1         # Leakage power of inverter in nW
 spice["nand2_leakage"] = 1       # Leakage power of 2-input nand in nW
 spice["nand3_leakage"] = 1       # Leakage power of 3-input nand in nW
+spice["nand4_leakage"] = 1       # Leakage power of 4-input nand in nW
 spice["nor2_leakage"] = 1        # Leakage power of 2-input nor in nW
 spice["dff_leakage"] = 1         # Leakage power of flop in nW