[libc][Obvious] Destroy the block store var in block store test.

Author: Siva Chandra Reddy

libc/test/src/__support/CPP/blockstore_test.cpp

@@ -38,6 +38,8 @@ class LlvmLibcBlockStoreTest : public __llvm_libc::testing::Test {
       }
     }
     ASSERT_EQ(i, int(ELEMENT_COUNT));
+    __llvm_libc::cpp::BlockStore<Element, BLOCK_SIZE, REVERSE>::destroy(
+        &block_store);
   }
 };