fix(tests): Ignores tarball that will change on dep update

The unit test added to cover #7233 was causing changes to show up in git
when tests were ran. This was due to the dependency build creating a new
tarball. These changes would cause a dirty build when we build our major
versions, so I removed the subchart tarball from git and added the charts
folder for that test chart to the gitignore to avoid any future problems.
Based on all I can see, this should have any impact on the test itself

Signed-off-by: Taylor Thomas <taylor.thomas@microsoft.com>

.gitignore

@@ -7,3 +7,5 @@
 _dist/
 bin/
 vendor/
+# Ignores charts pulled for dependency build tests
+cmd/helm/testdata/testcharts/issue-7233/charts/*