Remove constexprs from params in jit.py (#8536)

The `constexprs` field is never used outside `jit.py` and can be
computed on-demand from `self.params`. This addresses part of the
TODO(jlebar) at line 735.

Author: ita9naiwa

python/triton/runtime/jit.py

@@ -740,7 +740,6 @@ def __init__(self, fn, version=None, do_not_specialize=None, do_not_specialize_o
         # TODO(jlebar): Remove uses of these fields outside this file, then
         # remove the fields here.
         self.arg_names = [p.name for p in self.params]
-        self.constexprs = [p.num for p in self.params if p.is_constexpr]
 
         # Hooks that will be called prior to executing "run"
         self.pre_run_hooks = []