fix(ci): tidy module before linting

[manute]

Fixes #744

I think the root cause that is keep failing the CI is

go: updates to go.mod needed; to update it:
    go mod tidy
make[1]: *** [Makefile:101: lint_module_/home/runner/work/go-grpc-middleware/go-grpc-middleware/examples] Error 

Changes

So, I have just added a go mod tidy for each mod before linting in the makefile.

Verification

I tested locally and it works - let's see if here it works the CI

[johanbrandhorst]

Nice! Thanks!