cmd/gitserver: Initialise logger for vcsDependenciesSyncer

Created by: indradhanush

This is causing a panic because of a nil logger.

Also fixed a typo in the logger's description.

Error seen here: https://console.cloud.google.com/errors/detail/CJHhhqOpysjPVQ;time=P30D?project=sourcegraph-dev

Full error log:

runtime error: invalid memory address or nil pointer dereference [signal SIGSEGV: segmentation violation code=0x1 addr=0x50 pc=0x11dd51c]
at github.com/sourcegraph/sourcegraph/cmd/gitserver/server.(*vcsDependenciesSyncer).Fetch ( [github.com/sourcegraph/sourcegraph/cmd/gitserver/server/vcs_dependencies_syncer.go:110](https://console.cloud.google.com/debug?referrer=fromlog&file=github.com%2Fsourcegraph%2Fsourcegraph%2Fcmd%2Fgitserver%2Fserver%2Fvcs_dependencies_syncer.go&line=110&project=sourcegraph-dev) )
at github.com/sourcegraph/sourcegraph/cmd/gitserver/server.(*vcsDependenciesSyncer).CloneCommand ( [github.com/sourcegraph/sourcegraph/cmd/gitserver/server/vcs_dependencies_syncer.go:82](https://console.cloud.google.com/debug?referrer=fromlog&file=github.com%2Fsourcegraph%2Fsourcegraph%2Fcmd%2Fgitserver%2Fserver%2Fvcs_dependencies_syncer.go&line=82&project=sourcegraph-dev) )
at github.com/sourcegraph/sourcegraph/cmd/gitserver/server.(*Server).doClone ( [github.com/sourcegraph/sourcegraph/cmd/gitserver/server/server.go:2016](https://console.cloud.google.com/debug?referrer=fromlog&file=github.com%2Fsourcegraph%2Fsourcegraph%2Fcmd%2Fgitserver%2Fserver%2Fserver.go&line=2016&project=sourcegraph-dev) )
at github.com/sourcegraph/sourcegraph/cmd/gitserver/server.(*Server).cloneJobConsumer.func1 ( [github.com/sourcegraph/sourcegraph/cmd/gitserver/server/server.go:507](https://console.cloud.google.com/debug?referrer=fromlog&file=github.com%2Fsourcegraph%2Fsourcegraph%2Fcmd%2Fgitserver%2Fserver%2Fserver.go&line=507&project=sourcegraph-dev) )

Test plan

Existing tests should pass.