Make sigop limit `20000` just as in Bitcoin, ignoring our change to the blocksize limit.

src/consensus/consensus.h

@@ -9,7 +9,7 @@
 /** The maximum allowed size for a serialized block, in bytes (network rule) */
 static const unsigned int MAX_BLOCK_SIZE = 2000000;
 /** The maximum allowed number of signature check operations in a block (network rule) */
-static const unsigned int MAX_BLOCK_SIGOPS = MAX_BLOCK_SIZE/50;
+static const unsigned int MAX_BLOCK_SIGOPS = 20000;
 /** Coinbase transaction outputs can only be spent after this number of new blocks (network rule) */
 static const int COINBASE_MATURITY = 100;