Remove trailing space highlight and add highlight of redundant spaces

tests/reference/baseConfig_novelwriter.conf

@@ -55,6 +55,7 @@ spelltool = internal
 spellcheck = en
 showtabsnspaces = False
 showlineendings = False
+showmultispaces = True
 bigdoclimit = 800
 showfullpath = True
 highlightquotes = True

tests/reference/guiPreferences_novelwriter.conf

@@ -55,6 +55,7 @@ spelltool = internal
 spellcheck = en
 showtabsnspaces = True
 showlineendings = True
+showmultispaces = True
 bigdoclimit = 500
 showfullpath = False
 highlightquotes = False

tests/test_gui/test_gui_theme.py

@@ -109,7 +109,7 @@ def testGuiTheme_Main(qtbot, monkeypatch, nwMinimal, tmpDir):
     assert nwGUI.theTheme.colKey    == [242, 119, 122]
     assert nwGUI.theTheme.colVal    == [204, 153, 204]
     assert nwGUI.theTheme.colSpell  == [242, 119, 122]
-    assert nwGUI.theTheme.colTagErr == [153, 204, 153]
+    assert nwGUI.theTheme.colError  == [153, 204, 153]
     assert nwGUI.theTheme.colRepTag == [102, 204, 204]
     assert nwGUI.theTheme.colMod    == [249, 145, 57]