Bump core in local Makefile to 20.1.0 (#546) #596

Job	Run time
amd64 / build-stellar-friendbot	50s
amd64 / build-stellar-core	42s
amd64 / build-rs-stellar-xdr	2m 51s
amd64 / build-stellar-horizon	3m 7s
amd64 / build-stellar-soroban-rpc	1m 55s
arm64 / build-rs-stellar-xdr	3m 17s
arm64 / build-stellar-friendbot	4m 47s
arm64 / build-stellar-core	22s
arm64 / build-stellar-horizon	8m 39s
arm64 / build-stellar-soroban-rpc	3m 16s
amd64 / build	4m 24s
amd64 / test (pubnet)	1m 19s
amd64 / test (local)	1m 42s
amd64 / push-pr	0s
amd64 / test (local, --enable-soroban-rpc)	1m 55s
arm64 / build	9m 1s
amd64 / push-release	57s
arm64 / test (pubnet)	1m 13s
arm64 / test (local)	1m 45s
arm64 / test (local, --enable-soroban-rpc)	2m 51s
arm64 / push-pr	0s
arm64 / push-release	53s
manifest / push	4s
complete	1s
	55m 51s

Provide feedback