x/tools/gopls/internal/regtest/misc: TestFailingDiagnosticClearingOnEdit failures with "context deadline exceeded"

[dmitshur]

There are instances of the TestFailingDiagnosticClearingOnEdit test failing with "context deadline exceeded":

--- FAIL: TestFailingDiagnosticClearingOnEdit (560.80s)
    --- FAIL: TestFailingDiagnosticClearingOnEdit/default (560.80s)
        failures_test.go:63: waiting on:
            Met: no diagnostics for "a.go"
            Unmet: no diagnostics for "b.go"
            
            err:context deadline exceeded
            
            state:
            #### log messages (see RPC logs for full text):
            	Info: "2022/08/03 20:09:16 go env for /tmp/workdir/tmp/go...
            	Info: "2022/08/03 20:09:16 go/packages.Load #22\n\tsnapsh...
            	Info: "2022/08/03 20:09:16 go/packages.Load #22: updating...
            	Error: "2022/08/03 20:09:16 unable to compute positions f...
            	Error: "2022/08/03 20:09:16 unable to compute positions f...
            
            #### diagnostics:
            	b.go (version 1):
            
            #### outstanding work:
            #### completed work:
            	Load: 1
            	Setting up workspace: 1
            	diagnosing initial workspace load: 1
            	diagnosing opened files: 1
FAIL
FAIL	golang.org/x/tools/gopls/internal/regtest/misc	588.737s

• 2022-08-03T20:00:23-371fc67-f28fa95/freebsd-amd64-12_3
• 2022-08-03T20:00:23-371fc67-4345620/darwin-amd64-nocgo

[gopherbot]

Change https://go.dev/cl/422136 mentions this issue: gopls/internal/regtest: fix TestFailingDiagnosticClearingOnEdit