Fix IsolatedPrerender Probing Flakiness on Linux

Limiting the probe to a number of milliseconds is causing this to
flake about 5% of the time, and does nothing to help with test
timeouts. Removing the test-specific limit.

With this change, the test was not flaky at all after 100 interations
with --gtest_repeat

TBR=tbansal@chromium.org

TBR since it's outside normal working hours and I've already been
contacted by the flake sherrif once tonight...

Bug: 1023485
Change-Id: I20377999a1e3d5076cc861118ee84a514916d4b5
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2129239Reviewed-by: Robert Ogden <robertogden@chromium.org>
Commit-Queue: Robert Ogden <robertogden@chromium.org>
Auto-Submit: Robert Ogden <robertogden@chromium.org>
Cr-Commit-Position: refs/heads/master@{#754818}

chrome/browser/prerender/isolated/isolated_prerender_browsertest.cc

@@ -425,9 +425,8 @@ class ProbingEnabledIsolatedPrerenderBrowserTest
  public:
   void SetFeatures() override {
     IsolatedPrerenderBrowserTest::SetFeatures();
-    scoped_feature_list_.InitAndEnableFeatureWithParameters(
-        features::kIsolatePrerendersMustProbeOrigin,
-        {{"probe_timeout_ms", "100"}});
+    scoped_feature_list_.InitAndEnableFeature(
+        features::kIsolatePrerendersMustProbeOrigin);
   }
 
  private: