More explicit test of status panel content

Use Equals instead of Contains for asserting the status view content. This
solves the problem that we might assert Contains("↓2 repo"), but what it really
shows is "↑1↓2 repo", and the test still succeeds. At best this is confusing.

Also, this way we don't have to use the awkward DoesNotContain to check that it
really doesn't show a checkmark.

To do this, we need to fix two whitespace problems:
- there was always a space at the end for no reason. Simply remove it. It was
  added in efb51eee96, but from looking at that diff it seems it was added
  accidentally.
- there was a space at the beginning if the branch status was empty. This is
  actually a cosmetic problem, for branches without a status the text was
  indented by once space. Change this so that the space is added conditionally.
  It's a bit awkward that we have to use Decolorise here, but this will go away
  again later in this branch.

pkg/integration/tests/sync/force_push_multiple_matching.go

@@ -22,7 +22,7 @@ var ForcePushMultipleMatching = NewIntegrationTest(NewIntegrationTestArgs{
 				Contains("one"),
 			)
 
-		t.Views().Status().Content(Contains("↓1 repo → master"))
+		t.Views().Status().Content(Equals("↓1 repo → master"))
 
 		t.Views().Branches().
 			Lines(
@@ -42,7 +42,7 @@ var ForcePushMultipleMatching = NewIntegrationTest(NewIntegrationTestArgs{
 				Contains("one"),
 			)
 
-		t.Views().Status().Content(Contains("✓ repo → master"))
+		t.Views().Status().Content(Equals("✓ repo → master"))
 
 		t.Views().Branches().
 			Lines(