drop removePrefix as kotlinx.io doesn't have it in tags

Author: whyoleg

.teamcity/references/builds/kotlinx/io/KotlinxIOBuildApiReference.kt

@@ -10,7 +10,7 @@ import references.vcsRoots.KotlinxIO
 
 object KotlinxIOBuildApiReference : BuildApiPages(
     apiId = KOTLINX_IO_ID,
-    releaseTag = KOTLINX_IO_RELEASE_LABEL.removePrefix("v"),
+    releaseTag = KOTLINX_IO_RELEASE_LABEL,
     pagesRoot = "build/dokka/html",
     stepDokkaVersionSync = {
         // TODO readme, and disable this step for other libs too