update nebula-go to 2.5.1

[wey-gu]

else, the build will fail due to 2.5.0 checksum mismatch(used to be force pushed)

[wey-gu]

The build will fail due to it pull the latest and that is exactly why the PR was raised:

2021/10/19 08:10:15 [INFO] exec (timeout=0s): /opt/hostedtoolcache/go/1.16.4/x64/bin/go get -d -v github.com/vesoft-inc/k6-plugin@latest 
go: downloading github.com/vesoft-inc/k6-plugin v0.0.7
go: downloading github.com/vesoft-inc/nebula-go/v2 v2.5.0
github.com/vesoft-inc/k6-plugin imports
	github.com/vesoft-inc/nebula-go/v2: github.com/vesoft-inc/nebula-go/v2@v2.5.0: verifying module: checksum mismatch
	downloaded: h1:7w3bUYTAtvEA20go5XFoEDx5HbnzlOgo5VBSP3AvXtE=
	sum.golang.org: h1:A4wZoGqR1W1mQ9y/X+tV1wCMIsDkuhFMthTQKMeT8Yc=

SECURITY ERROR
This download does NOT match the one reported by the checksum server.
The bits may have been replaced on the origin server, or an attacker may
have intercepted the download attempt.

For more information, see 'go help module-auth'.

2021/10/19 08:10:22 [FATAL] exit status 1
Error: make: *** [Makefile:24: build-arm-v7] Error 1
Error: Process completed with exit code 2.