[lit] Remove unused variable in googletest format

Summary: `prefix` is written to but never read.

Reviewers: echristo, delcypher, beanz, ddunbar

Subscribers: llvm-commits, mehdi_amini

Differential Revision: https://reviews.llvm.org/D25408

llvm-svn: 283706

llvm/utils/lit/lit/formats/googletest.py

@@ -52,7 +52,6 @@ class GoogleTest(TestFormat):
                 # handle it here in case upstream googletest is being used.
                 continue
 
-            prefix = ''
             index = 0
             while ln[index*2:index*2+2] == '  ':
                 index += 1