util: Remove RandAddSeedPerfmon

RegQueryValueExA(HKEY_PERFORMANCE_DATA, ...) sometimes hangs bitcoind.exe on Windows during startup, at least on CI.

We have other sources of entropy to seed randomness with on Windows, so should be alright removing this. Might resurrect if less drastic fix is found.

src/random.h

@@ -49,7 +49,7 @@
  *
  * - RandAddPeriodic() seeds everything that fast seeding includes, but additionally:
  *   - A high-precision timestamp
- *   - Dynamic environment data (performance monitoring, ...)
+ *   - Dynamic environment data (clocks, resource usage, ...)
  *   - Strengthen the entropy for 10 ms using repeated SHA512.
  *   This is run once every minute.
  *