Use cache-first as fetchPolicy for webhook logs

[pjlast]

Closes #44720

The default policy is 'network-only': https://sourcegraph.com/github.com/sourcegraph/sourcegraph/-/blob/client/http-client/src/graphql/apollo/client.ts?L68

This is different from what the Apollo docs will tell you, because this is our own implementation.

This is what's causing the double requests. However, this should not reload the entire page, it simply determines how the final data is fetched. From what I can gather, the reloading (or rather, the replacing of the combined data with the initial data) is a bug in apollo <3.6 when using the network-only policy (and we're using apollo version 3.5): apollographql/apollo-client#6916

One option is to update the apollo client version, but this feels risky given that we don't know if there could be other regressions that happen because of it. Instead, this PR sets the fetchPolicy to cache-first instead (which is recommended in that thread, and also how we handle it in other parts of the code base).

Test plan

Confirmed to work manually

App preview:

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[sashaostrikov]

LGTM!
PR description diff is 10 times longer than the code diff 😁
We should document this stuff somewhere, because it is very implicit IMHO

[sg-e2e-regression-test-bob]

Bundle size report 📦

Initial size	Total size	Async size	Modules
0.00% (0.00 kb)	0.00% (+0.04 kb)	0.00% (+0.04 kb)	0.00% (0)

Look at the Statoscope report for a full comparison between the commits 31f1294 and 7794a49 or learn more.

Open explanation

• Initial size is the size of the initial bundle (the one that is loaded when you open the page)
• Total size is the size of the initial bundle + all the async loaded chunks
• Async size is the size of all the async loaded chunks
• Modules is the number of modules in the initial bundle