ConversionHostTest: re-enable unit test

This reverts
https://chromium-review.googlesource.com/c/chromium/src/+/2626687
as Impression::impression_data is initialized due to
https://chromium-review.googlesource.com/c/chromium/src/+/2625293

Bug: 1165985
Change-Id: I6dbcb17c9f1f31487e2f1ba3b2da6febd906a8ce
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2627190
Auto-Submit: Eric Willigers <ericwilligers@chromium.org>
Commit-Queue: John Delaney <johnidel@chromium.org>
Reviewed-by: John Delaney <johnidel@chromium.org>
Cr-Commit-Position: refs/heads/master@{#843660}

content/browser/conversions/conversion_host_unittest.cc

@@ -355,9 +355,8 @@ TEST_F(ConversionHostTest,
   EXPECT_EQ(0u, test_manager_.num_impressions());
 }
 
-// TODO(crbug.com/1165985): Fix Linux ChromiumOS MSan Tests
 TEST_F(ConversionHostTest,
-       DISABLED_ImpressionNavigation_OriginTrustworthyChecksPerformed) {
+       ImpressionNavigation_OriginTrustworthyChecksPerformed) {
   const char kLocalHost[] = "http://localhost";
 
   struct {