simplify declaration iteration

Co-authored-by: Michael Bryant <mbryant@rigetti.com>

pyquil/quil.py

@@ -183,7 +183,7 @@ def copy_everything_except_instructions(self) -> "Program":
  """
  new_prog = Program()
  new_prog._calibrations = self.calibrations.copy()
- for _, declaration in self.declarations.items():
+ for declaration in self.declarations.values():
  new_prog.inst(declaration)
  new_prog._declarations = self._declarations.copy()
  new_prog._waveforms = self.waveforms.copy()