Update default Git version to v2.53.0.vfs.0.5 in CI/PR builds

[mjcheetham]

Let's bump the default microsoft/git version that we build and test against in CI/PR runs to the current latest pre-release (v2.50.1.vfs.0.1 -> v2.53.0.vfs.0.5).

Note that the current full-release (v2.53.0.vfs.0.0) has bugs that prevent successful functional test runs, hence switching to a pre-release.

[mjcheetham]

@tyrielv it looks like there's an issue with v2.53.0.vfs.0.0 that is causing three functional tests to fail:

1) Failed : GVFS.FunctionalTests.Tests.EnlistmentPerFixture.GitCorruptObjectTests.GitRequestsReplacementForAllNullObject()
  Expected: 0
  But was:  128
   at GVFS.Tests.Should.ValueShouldExtensions.ShouldEqual[T](T actualValue, T expectedValue, String message)
   at GVFS.FunctionalTests.Tests.EnlistmentPerFixture.GitCorruptObjectTests.RunGitResetHardWithCorruptObject(Action`1 corruptObject)
   at GVFS.FunctionalTests.Tests.EnlistmentPerFixture.GitCorruptObjectTests.GitRequestsReplacementForAllNullObject()

2) Failed : GVFS.FunctionalTests.Tests.EnlistmentPerFixture.GitCorruptObjectTests.GitRequestsReplacementForObjectCorruptedWithBadData()
  Expected string length 0 but was 469. Strings differ at index 0.
  Expected: <string.Empty>
  But was:  "# GVFS\r\n\r\nThis is a conflict for the rebase test\r\n\r\n## What i..."
  -----------^
   at GVFS.Tests.Should.ValueShouldExtensions.ShouldEqual[T](T actualValue, T expectedValue, String message)
   at GVFS.FunctionalTests.Tests.EnlistmentPerFixture.GitCorruptObjectTests.RunGitCatFileWithCorruptObject(Action`1 corruptObject)
   at GVFS.FunctionalTests.Tests.EnlistmentPerFixture.GitCorruptObjectTests.GitRequestsReplacementForObjectCorruptedWithBadData()

3) Failed : GVFS.FunctionalTests.Tests.EnlistmentPerFixture.GitCorruptObjectTests.GitRequestsReplacementForTruncatedObject()
  The contents of C:\Repos\GVFSFunctionalTests\enlistment\3618f73a41eb474c9082\src\Readme.md do not match what was expected
  Expected string length 0 but was 469. Strings differ at index 0.
  Expected: <string.Empty>
  But was:  "# GVFS\r\n\r\nThis is a conflict for the rebase test\r\n\r\n## What i..."
  -----------^
   at GVFS.Tests.Should.ValueShouldExtensions.ShouldEqual[T](T actualValue, T expectedValue, String message)
   at GVFS.FunctionalTests.Should.FileSystemShouldExtensions.FileAdapter.WithContents(String expectedContents)
   at GVFS.FunctionalTests.Tests.EnlistmentPerFixture.GitCorruptObjectTests.RunGitResetHardWithCorruptObject(Action`1 corruptObject)
   at GVFS.FunctionalTests.Tests.EnlistmentPerFixture.GitCorruptObjectTests.GitRequestsReplacementForTruncatedObject()

[dscho]

Nice!