wiki/images: remove release-cycle.svg prefers-color-scheme

This seems to interfere with the website's css and its
own dark mode theme control.

For golang/go#65059

Change-Id: I1aedeb7c177ae81b9e9a49452b9b7a2f87ca884f
Reviewed-on: https://go-review.googlesource.com/c/wiki/+/558660
Commit-Queue: Hyang-Ah Hana Kim <hyangah@gmail.com>
Reviewed-by: Hyang-Ah Hana Kim <hyangah@gmail.com>
diff --git a/images/release-cycle.svg b/images/release-cycle.svg
index bed9a96..4ea560b 100644
--- a/images/release-cycle.svg
+++ b/images/release-cycle.svg
@@ -12,14 +12,6 @@
 	stroke: black;
 	fill: none;
 }
-@media (prefers-color-scheme: dark) {
-	text {
-		fill: white;
-	}
-	line, path {
-		stroke: white;
-	}
-}
 ]]>
 </style>
 <g transform="translate(300,200)">