Remove obsolete nighttime theme

Better to do change the background colour with a palette

themes/tiddlywiki/nighttime/base.tid

@@ -1,8 +0,0 @@
-title: $:/themes/tiddlywiki/nighttime/base
-tags: [[$:/tags/stylesheet]]
-
-\rules only filteredtranscludeinline transcludeinline macrodef macrocallinline
-
-html body.tw-body {
-	background-color: #5C5D8E;
-}

themes/tiddlywiki/nighttime/plugin.info

@@ -1,9 +0,0 @@
-{
-	"title": "$:/themes/tiddlywiki/nighttime",
-	"name": "Night-time",
-	"author": "JeremyRuston",
-	"core-version": ">=5.0.0",
-	"plugin-type": "theme",
-	"description": "A darker theme",
-	"dependents": ["$:/themes/tiddlywiki/vanilla"]
-}