doc: remove usages of C++11

Now it's just the standard library.

src/random.cpp

@@ -62,7 +62,7 @@ static inline int64_t GetPerformanceCounter() noexcept
     __asm__ volatile ("rdtsc" : "=a"(r1), "=d"(r2)); // Constrain r1 to rax and r2 to rdx.
     return (r2 << 32) | r1;
 #else
-    // Fall back to using C++11 clock (usually microsecond or nanosecond precision)
+    // Fall back to using standard library clock (usually microsecond or nanosecond precision)
     return std::chrono::high_resolution_clock::now().time_since_epoch().count();
 #endif
 }
@@ -438,7 +438,7 @@ public:
 
 RNGState& GetRNGState() noexcept
 {
-    // This C++11 idiom relies on the guarantee that static variable are initialized
+    // This idiom relies on the guarantee that static variable are initialized
     // on first call, even when multiple parallel calls are permitted.
     static std::vector<RNGState, secure_allocator<RNGState>> g_rng(1);
     return g_rng[0];