Adds GIT_AUTHOR_NAME to the test env (#6825)

## What's the problem this PR addresses?

The test env doesn't automatically setup the git committer name / email.
I noticed it when working on `yarn init`, as the test was passing but I
didn't understand why until I dig deeper (turns out we don't pass the
`strict` flag when calling the `git` commands; I don't remember whether
it's an oversight or not).

## How did you fix it?

Automatically setup the git committer name / email. Should a test want
to avoid that (for example to explicitly test that a command works
without), they should override it manually.

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Author: arcanis

packages/acceptance-tests/pkg-tests-core/sources/utils/makeTemporaryEnv.ts

@@ -56,6 +56,11 @@ const mte = generatePkgDriver({
         [`YARN_PNP_FALLBACK_MODE`]: `none`,
         // Otherwise tests fail on systems where this is globally set to true
         [`YARN_ENABLE_GLOBAL_CACHE`]: `false`,
+        // To make sure we can call Git commands
+        [`GIT_AUTHOR_NAME`]: `John Doe`,
+        [`GIT_AUTHOR_EMAIL`]: `[email protected]`,
+        [`GIT_COMMITTER_NAME`]: `John Doe`,
+        [`GIT_COMMITTER_EMAIL`]: `[email protected]`,
         // Older versions of Windows need this set to not have node throw an error
         [`NODE_SKIP_PLATFORM_CHECK`]: `1`,
         // We don't want the PnP runtime to be accidentally injected