scripted-diff: validation: rename mandatory errors into block errors

Using "block" or "mempool" as the prefix in place of "mandatory" or "non-mandatory" is clearer
to a user. "non-mandatory" was renamed into "mempool" as part of #33050. This takes care of the
other half of this renaming as a scripted diff.

-BEGIN VERIFY SCRIPT-
sed -i 's/mandatory-script-verify/block-script-verify/g' $(git grep -l mandatory-script-verify)
-END VERIFY SCRIPT-

test/functional/feature_cltv.py

@@ -153,7 +153,7 @@ class BIP65Test(BitcoinTestFramework):
             coin_vout = coin.prevout.n
             cltv_invalidate(spendtx, i)
 
-            blk_rej = "mandatory-script-verify-flag-failed"
+            blk_rej = "block-script-verify-flag-failed"
             tx_rej = "mempool-script-verify-flag-failed"
             expected_cltv_reject_reason = [
                 " (Operation not valid with the current stack size)",