build: bump version to v0.3.1-alpha #1789

Job	Run time
cross compilation	18m 8s
Format check	55s
Docker build check	5m 28s
Compilation check	2m 26s
run itests	9m 42s
run itests postgres	12m 44s
Lint check	2m 15s
go mod check	39s
RPC check	1m 43s
Sqlc check	19s
test vector check	2m 10s
run unit tests (unit-race)	6m 39s
run unit tests (unit-cover)	2m 49s
run unit tests (unit dbbackend=postgres)	5m 21s
	1h 11m 18s

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