sky130_sram_macros has syntax error

[M0stafaRady]

'mem' reg in the models are defined after it is used so it needed to be declared. it give the following error:

Error-[IND] Identifier not declared
/home/karim/actions-runner-2/_work/Cheetah_V3/Cheetah_V3/dependencies/pdks/sky130A/libs.ref/sky130_sram_macros/verilog/sky130_sram_2kbyte_1rw1r_32x512_8.v, 59
  Identifier 'mem' has not been declared yet. If this error is not expected, 
  please check if you have set `default_nettype to none.