tests: stabilize test-extdiff.t on Windows The test harness only wanted to drop the (windows !) lines, which also means the actual output matched the (no-windows !) lines. So drop those annotations too. I suspect if the output of the affected tests was actually collected on Windows, things were quoted because TEMPDIR contained a `~` in MSYS. Typically that happens when the username is 9 (8?) or more characters. I explicitly set TEMP and TMP to something short like "C:\temp" to avoid this, because otherwise there are a bunch of failures like this in other tests.

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    "base": "hg:.^"
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