Latest version incompatible with older GitHub Enterprise Server usages.

[yaneury]

#347 added Merge Queue support for this tool. Unfortunately, it seems that this change is incompatible with Github Enterprise Servers that don't have this feature enable (I believe it was just released this past July). When running the tool, we get the following panic:

panic: query PullRequests.viewer.pullRequests.nodes.mergeQueueEntry: Field 'mergeQueueEntry' doesn't exist on type 'PullRequest'

goroutine 1 [running]:
github.com/ejoffe/spr/github/githubclient.check({0x104f1fca8, 0x1400000e6d8})
       .../spr/github/githubclient/client.go:671 +0xe8
github.com/ejoffe/spr/github/githubclient.(*client).GetInfo(0x1400019c9a8, {0x104f23410?, 0x105239160?}, {0x104f23330, 0x1400019c978})
        .../spr/github/githubclient/client.go:183 +0xc0
github.com/ejoffe/spr/spr.(*stackediff).fetchAndGetGitHubInfo(0x140001a4de0, {0x104f23410, 0x105239160})
       .../spr/spr/spr.go:490 +0x14c
github.com/ejoffe/spr/spr.(*stackediff).UpdatePullRequests(0x140001a4de0, {0x104f23410?, 0x105239160}, {0x0, 0x0, 0x0}, 0x0)
       .../spr/spr/spr.go:137 +0x70
...

Is there a way to make this query optional such that the tool remains compatible with older Github Enterprise instances? I'm happy to submit a PR to do so, but am not too familiar with how to accomplish this in GraphQL.

[ejoffe]

I'll look into this when I have some spare cycles, should be fairly easy to feature flag the merge queue feature.

[ejoffe]

Fix released in v0.14.5