Remove redundant import

Author: lcartey

c/cert/src/rules/PRE31-C/SideEffectsInArgumentsToUnsafeMacros.ql

@@ -15,7 +15,6 @@ import cpp
 import codingstandards.c.cert
 import codingstandards.cpp.Macro
 import codingstandards.cpp.SideEffect
-import codingstandards.cpp.StructuralEquivalence
 import codingstandards.cpp.sideeffect.DefaultEffects
 import codingstandards.cpp.sideeffect.Customizations
 import semmle.code.cpp.valuenumbering.HashCons