Fix sign conversion warning from clang:

googletest/samples/prime_tables.h:81:57: error:
implicit conversion changes signedness: 'int' to 'unsigned long'
[-Werror,-Wsign-conversion]
      : is_prime_size_(max + 1), is_prime_(new bool[max + 1]) {
                                           ~~~      ~~~~^~~

PiperOrigin-RevId: 506065360
Change-Id: Ida4550562531012c089e2f9fcf530b3a78889fa3

googletest/samples/prime_tables.h

@@ -78,8 +78,9 @@ class PreCalculatedPrimeTable : public PrimeTable {
  public:
   // 'max' specifies the maximum number the prime table holds.
   explicit PreCalculatedPrimeTable(int max)
-      : is_prime_size_(max + 1), is_prime_(new bool[max + 1]) {
-    CalculatePrimesUpTo(max);
+      : is_prime_size_(std::max(1, max + 1)),
+        is_prime_(new bool[static_cast<size_t>(is_prime_size_)]) {
+    CalculatePrimesUpTo(is_prime_size_ - 1);
   }
   ~PreCalculatedPrimeTable() override { delete[] is_prime_; }