makefile: for make release-src, it should release the source code

[membphis]

https://github.com/apache/apisix-dashboard/blob/v2.0/Makefile#L93

that is wrong, for make release-src, it should release the source code.

but we released binary file now, this is wrong.

.PHONY: release-src
release-src:
	tar –cf dashboard.tar ./output/*

[membphis]

@gxthrj you can take a look at this issue

[gxthrj]

ok, we can call it make release,the release package contains the binary file of manager-api and static files of web.

[juzhiyuan]

make-release is more semantic and clearer.

[gxthrj]

@membphis Can we close this issue now?
The document has changed the original purpose of packaging the output directory.
make release-src is for source release now. #816

[juzhiyuan]

We could close this one IMO.