Add 'testing' to a path that got missed

This applies the proper configuration rules the end HTML generation.

Bug:
Change-Id: Ica159131e574fd805a1363db5b26a6581ecc0ac6
Reviewed-on: https://pdfium-review.googlesource.com/10810
Reviewed-by: Henrique Nakashima <hnakashima@chromium.org>
Commit-Queue: Ryan Harrison <rharrison@chromium.org>
diff --git a/testing/tools/coverage/coverage_report.py b/testing/tools/coverage/coverage_report.py
index c12e6cd..95c88bf 100755
--- a/testing/tools/coverage/coverage_report.py
+++ b/testing/tools/coverage/coverage_report.py
@@ -292,7 +292,7 @@
   def generate_report(self):
     """Produce HTML coverage report based on combined coverage data set."""
     config_file = os.path.join(
-        self.source_directory, 'tools', 'coverage', 'lcovrc')
+        self.source_directory, 'testing', 'tools', 'coverage', 'lcovrc')
 
     lcov_args = ['genhtml',
       '--config-file', config_file,