PIP-35 for amoy: enforce 25gwei gas config for amoy for erigon 2 (#11…

…078)

Cherry picks erigontech/erigon#11077

> A followup PR to erigontech/erigon#10119
which sets the fields `txpool.pricelimit`, `miner.gasprice` and
`gpo.ignoreprice` to 25gwei only for polygon amoy network.
> Upon sufficient announcements, it will be generalised to all polygon
chains later.

txpool/txpoolcfg/txpoolcfg.go

@@ -30,7 +30,7 @@ import (
 )
 
 // BorDefaultTxPoolPriceLimit defines the minimum gas price limit for bor to enforce txs acceptance into the pool.
-const BorDefaultTxPoolPriceLimit = 30 * common.GWei
+const BorDefaultTxPoolPriceLimit = 25 * common.GWei
 
 type Config struct {
 	DBDir               string