Drop : after extension in docs and dokka tests

Author: odersky

docs/docs/reference/contextual/extension-methods.md

@@ -103,7 +103,7 @@ a single extension and enclose all methods in braces or an indented region follo
 Example:
 
 ```scala
-extension (ss: Seq[String]):
+extension (ss: Seq[String])
 
   def longestStrings: Seq[String] =
     val maxLength = ss.map(_.length).max

scala3doc/src/dotty/dokka/model/api/membersUtils.scala

@@ -5,7 +5,7 @@ import scala.jdk.CollectionConverters.{ListHasAsScala, SeqHasAsJava}
 import dotty.dokka.model.api._
 
 extension (m: DModule)
-  def visitMembers(callback: Member => Unit): Unit = 
+  def visitMembers(callback: Member => Unit): Unit =
     def visitClasslike(c: Member): Unit =
       callback(c)
       c.allMembers.foreach(visitClasslike(_))
@@ -16,12 +16,12 @@ extension (s: Signature)
     s.map {
       case s: String => s
       case l: Link => l.name
-    }.mkString 
+    }.mkString
 
-extension (m: Member):
+extension (m: Member)
   def getDirectParentsAsStrings: Seq[String] =
     m.directParents.map(_.getName).sorted
   def getParentsAsStrings: Seq[String] =
     m.parents.map(_.signature.getName).sorted
-  def getKnownChildrenAsStrings: Seq[String] =   
+  def getKnownChildrenAsStrings: Seq[String] =
     m.knownChildren.map(_.signature.getName).sorted