Add note about resources with pubnet #517

Job	Run time
amd64 / build-stellar-core	27s
amd64 / build-stellar-friendbot	52s
amd64 / build-stellar-horizon	2m 13s
amd64 / build-stellar-soroban-rpc	57s
arm64 / build-stellar-core	26s
arm64 / build-stellar-friendbot	2m 56s
arm64 / build-stellar-horizon	8m 1s
arm64 / build-stellar-soroban-rpc	44s
amd64 / build	3m 43s
amd64 / test (pubnet)	1m 41s
amd64 / push-pr	41s
amd64 / test (local)	1m 43s
amd64 / push-release	0s
arm64 / build	6m 49s
arm64 / test (pubnet)	1m 18s
arm64 / test (local)	2m 21s
arm64 / push-pr	48s
arm64 / push-release	0s
manifest / push	5s
complete	1s
	35m 46s

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