Fix links to resolve issue in Builder's Guide (https and redirect) #15781

Job	Run time
RPC and mobile compilation check	5m 37s
Sqlc check	5m 1s
check commits	5m 44s
cross compilation	33m 49s
lint code	7m 47s
sample configuration check	3m 21s
run unit tests (btcd unit-cover)	17m 31s
check pinned dependencies (google.golang.org/grpc v1.59.0)	3s
run unit tests (unit tags="kvdb_etcd")	19m 47s
check pinned dependencies (github.com/golang/protobuf v1.5.3)	6s
run unit tests (unit tags="kvdb_postgres")	18m 30s
run unit tests (unit tags="kvdb_sqlite")	17m 9s
run windows itest	31m 34s
run ubuntu itests (btcd, backend=btcd cover=1)	34m 18s
run ubuntu itests (bitcoind, backend=bitcoind cover=1)	42m 30s
run unit tests (btcd unit-race)	35m 33s
run ubuntu itests (bitcoind-notxindex, backend="bitcoind notxindex")	42m 25s
run unit tests (unit-module)	4m 34s
run ubuntu itests (bitcoind-rpcpolling, backend="bitcoind rpcpolling" cover=1)	42m 19s
run ubuntu itests (bitcoind-etcd, backend=bitcoind dbbackend=etcd)	54m 53s
run ubuntu itests (bitcoind-postgres, backend=bitcoind dbbackend=postgres)	1h 13m 7s
run macOS itest	51m 0s
run ubuntu itests (bitcoind-sqlite, backend=bitcoind dbbackend=sqlite)	44m 11s
check release notes updated	3s
run ubuntu itests (bitcoind-postgres-nativesql, backend=bitcoind dbbackend=postgres nativesql=true)	1h 18m 42s
run ubuntu itests (bitcoind-sqlite-nativesql, backend=bitcoind dbbackend=sqlite nativesql=true)	44m 24s
run ubuntu itests (neutrino, backend=neutrino cover=1)	39m 24s
finish	5s
	12h 33m 27s

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