[lit] Remove unused TestingProgressDisplay attr

Summary:
`TestingProgressDisplay` initializes its `current` attribute to `None`, but
never reads or writes the value again. Remove it.

Reviewers: echristo, delcypher, beanz, ddunbar

Subscribers: llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D25415

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@283709 91177308-0d34-0410-b5e6-96231b3b80d8

utils/lit/lit/main.py

@@ -28,7 +28,6 @@ class TestingProgressDisplay(object):
     def __init__(self, opts, numTests, progressBar=None):
         self.opts = opts
         self.numTests = numTests
-        self.current = None
         self.progressBar = progressBar
         self.completed = 0