Bug 1693814 - Reenable some arena allocator tests on ccov builds since they no longer fail. r=jmaher DONTBUILD

Differential Revision: https://phabricator.services.mozilla.com/D105785

xpcom/tests/gtest/TestArenaAllocator.cpp

@@ -118,7 +118,6 @@ TEST(ArenaAllocator, AllocateLargerThanArenaSize)
   EXPECT_EQ(uintptr_t(x) + 8, uintptr_t(y));
 }
 
-#ifndef MOZ_CODE_COVERAGE
 TEST(ArenaAllocator, AllocationsPerChunk)
 {
   // Test that expected number of allocations fit in one chunk.
@@ -192,7 +191,6 @@ TEST(ArenaAllocator, MemoryIsValid)
     EXPECT_EQ(x[i], kMark);
   }
 }
-#endif
 
 MOZ_DEFINE_MALLOC_SIZE_OF(TestSizeOf);