Undo a temporary workaround in UnownedPtr.

The workaround is no longer needed since Clang fixed the issue that made
ProbeForLowSeverityLifetimeIssue() fail.

BUG=chromium:929475

Change-Id: I71fbbc1aa86002b4533936a53858a112a38f7a12
Reviewed-on: https://pdfium-review.googlesource.com/c/pdfium/+/52470
Reviewed-by: Tom Sepez <tsepez@chromium.org>
Commit-Queue: Lei Zhang <thestig@chromium.org>

core/fxcrt/unowned_ptr.h

diff --git a/core/fxcrt/unowned_ptr.h b/core/fxcrt/unowned_ptr.h
index 8be3bd3..0a44f9d 100644
--- a/core/fxcrt/unowned_ptr.h
+++ b/core/fxcrt/unowned_ptr.h
@@ -107,7 +107,7 @@
   inline void ProbeForLowSeverityLifetimeIssue() {
 #if defined(MEMORY_TOOL_REPLACES_ALLOCATOR)
     if (m_pObj)
-      (void)reinterpret_cast<const volatile uint8_t*>(m_pObj)[0];
+      reinterpret_cast<const volatile uint8_t*>(m_pObj)[0];
 #endif
   }