remove duplicate standard import from test script

tests/generator_scripts/scripts/SimpleClasses.py

 from pystencilssfg import SourceFileGenerator
 
 with SourceFileGenerator() as sfg:
-
-    sfg.include("<cstdint>")
-
     sfg.klass("Point")(
         sfg.public(
             sfg.method("getX", returns="const int64_t &", const=True, inline=True)(