Also update phi counts in adce pass

[Keno]

The whole point of this pass is to compute and compare the counts of all SSA value uses vs those of only-phi uses to find SSA values that have no real uses. In #47080, I updated the code to properly account for removal of phi edges in the SSA count, but neglected to do the same in the phi-only count, leading to #47180. Fix that.

Fixes #47180

[giordano]

For what is worth, by playing a bit more with creduce (more specifically, searching for "TypeError: in new" instead of the full message "TypeError: in new, expected Base.AbstractCmd, got a value of type Nothing", to give it more freedom) I've got a marginally simpler reproducer:

julia> function a(b)
           c = setenv(``, b.env)
           if true
               c = (c, )
           end
           c
       end
a (generic function with 1 method)

julia> a(``)
ERROR: TypeError: in new, expected Cmd, got a value of type Nothing
Stacktrace:
 [1] a(b::Cmd)
   @ Main ./REPL[1]:4
 [2] top-level scope
   @ REPL[2]:1

Suggested change

	# Issue #47180, incorrect phi counts in CmdRedirect
	function a47180(b; stdout )
	c = setenv(b, b.env)
	if true
	c = pipeline(c, stdout)
	end
	c
	end
	@test isa(a47180(``; stdout), Base.AbstractCmd)
	# Issue #47180, incorrect phi counts in Cmd
	function a47180(b)
	c = setenv(``, b.env)
	if true
	c = (c, )
	end
	c
	end
	@test isa(a47180(``), Tuple{Cmd})