Merge #15183: [Qt]: fixes m_assumed_blockchain_size variable value

8c3fdd3 fixes m_assumed_blockchain_size variables values: (marcoagner)

Pull request description:

  This is used by Qt but I'm not sure if this is the right tag here.
  Please, edit the title if there's something better.

  `m_assumed_blockchain_size` (src/chainparams.cpp:CChainParams) was
  `BLOCK_CHAIN_SIZE` (src/qt/intro.cpp) and while the transition was being
  made by PR 13216 (merged commit: 9d0e528), 3fc2063 changed its value
  from 200 to 220, which 9d0e528 ended up reverting.

  So, as per MarcoFalke's suggestion (bitcoin/bitcoin#13216 (comment)), I'm bumping it to 240 before 0.18 is
  branched to avoid any confusion.

  Anything else (e.g. constexpr) that should/could be done here? Thanks.

Tree-SHA512: 4319739b870a2b96a57f268f9edc7dd9f9eff5c4ca3b01863e6b861b9ca58c245416ce362dae54d1673e3d5b1c7f5a16e4031842af250e1b1f0a5109b75fb3c3

Author: MarcoFalke

src/chainparams.cpp

@@ -107,7 +107,7 @@ class CMainParams : public CChainParams {
         pchMessageStart[3] = 0xd9;
         nDefaultPort = 8333;
         nPruneAfterHeight = 100000;
-        m_assumed_blockchain_size = 200;
+        m_assumed_blockchain_size = 240;
         m_assumed_chain_state_size = 3;
 
         genesis = CreateGenesisBlock(1231006505, 2083236893, 0x1d00ffff, 1, 50 * COIN);
@@ -219,7 +219,7 @@ class CTestNetParams : public CChainParams {
         pchMessageStart[3] = 0x07;
         nDefaultPort = 18333;
         nPruneAfterHeight = 1000;
-        m_assumed_blockchain_size = 20;
+        m_assumed_blockchain_size = 30;
         m_assumed_chain_state_size = 2;
 
         genesis = CreateGenesisBlock(1296688602, 414098458, 0x1d00ffff, 1, 50 * COIN);