valuetest: fix potential write of terminating nul past the end of the…

… destination

Fixes 2 compile errors with gcc-12, eg:

tesunittest/valuetest.cpp:1516:30: error: 'sprintf' may write a terminating nul past the end of the destination [-Werror=format-overflow=]
test/unittest/valuetest.cpp:1516:20: note: 'sprintf' output between 2 and 11 bytes into a destination of size 10

test/unittest/valuetest.cpp

@@ -1581,7 +1581,7 @@ TEST(Value, ObjectHelperRangeFor) {
     {
         int i = 0;
         for (auto& m : x.GetObject()) {
-            char name[10];
+            char name[11];
             sprintf(name, "%d", i);
             EXPECT_STREQ(name, m.name.GetString());
             EXPECT_EQ(i, m.value.GetInt());
@@ -1592,7 +1592,7 @@ TEST(Value, ObjectHelperRangeFor) {
     {
         int i = 0;
         for (const auto& m : const_cast<const Value&>(x).GetObject()) {
-            char name[10];
+            char name[11];
             sprintf(name, "%d", i);
             EXPECT_STREQ(name, m.name.GetString());
             EXPECT_EQ(i, m.value.GetInt());