Drop a check for ext4 filesystem already selected

This has not been hit for a year (on stg; three years on prod).
I *think* it would only be hit if we ran the test on an Everything
image, but as the test is now specifically associated with the
Server install DVD, that doesn't seem likely to happen.

If we somehow *do* hit ext4 pre-selected again, this can still
be handled simply by adding an alternate
anaconda_blivet_part_fs_ext4 needle which matches on ext4 already
being selected; that avoids the need to keep an alternate code
path around.

Signed-off-by: Adam Williamson <awilliam@redhat.com>

needles/anaconda/partitioning/blivet/anaconda_blivet_part_fs_ext4_selected-20200507.json

@@ -1,17 +0,0 @@
-{
-  "area": [
-    {
-      "xpos": 320,
-      "ypos": 419,
-      "type": "match",
-      "width": 171,
-      "height": 24
-    }
-  ],
-  "properties": [],
-  "tags": [
-    "LANGUAGE-english",
-    "anaconda_blivet_part_fs",
-    "anaconda_blivet_part_fs_ext4_selected"
-  ]
-}

tests/disk_custom_blivet_btrfs_preserve_home.pm

@@ -47,11 +47,8 @@ sub run {
     assert_and_click "anaconda_blivet_part_edit";
     # Select the Format option
     assert_and_click "anaconda_blivet_part_format";
-    # Open the filesystem types and select ext4, if not selected
-    if (not(check_screen "anaconda_blivet_part_fs_ext4_selected", 30)) {
-        assert_and_click "anaconda_blivet_part_fs_select";
-        assert_and_click "anaconda_blivet_part_fs_ext4";
-    }
+    assert_and_click "anaconda_blivet_part_fs_select";
+    assert_and_click "anaconda_blivet_part_fs_ext4";
     # Select the mountpoint field
     send_key_until_needlematch("anaconda_blivet_mountpoint_selected", "tab", 3, 5);
     # Fill in the mountpoint