Conform foreach tparam to majority naming convention

'U' is the common choice for the foreach function result tparam.

This command summarises the naming diversity before and after this change.

$ fgrep -r 'def foreach[' *|cut -f2 -d:|cut -f1 -d'('|tr -s ' '|sed 's/override //g'|sort|uniq -c|sort -nr

Before,

     80  def foreach[U]
      6  def foreach[C]
      6  def foreach[B]
      4  final def foreach[U]
      3  def foreach[S]
      2  inline final def foreach[U]
      2  def foreach[A]
      1  inline final def foreach[specialized
      1  final def foreach[B]
      1  * def foreach[U]
      1  def foreach[Q]
      1  def foreach[D]
      1  def foreach[A,B,U]

After,

     98  def foreach[U]
      5  final def foreach[U]
      2  inline final def foreach[U]
      1  inline final def foreach[specialized
      1  * def foreach[U]
      1  def foreach[A,B,U]

(@ symbols removed.)

1 files changed, 1 insertions, 1 deletions

diff --git a/src/library/scala/collection/TraversableProxyLike.scala b/src/library/scala/collection/TraversableProxyLike.scala
index 4399dbc289..fa470ea238 100644
--- a/src/library/scala/collection/TraversableProxyLike.scala
+++ b/src/library/scala/collection/TraversableProxyLike.scala
@@ -28,7 +28,7 @@ import scala.reflect.ClassTag
 trait TraversableProxyLike[+A, +Repr <: TraversableLike[A, Repr] with Traversable[A]] extends TraversableLike[A, Repr] with Proxy {
   def self: Repr
 
-  override def foreach[B](f: A => B): Unit = self.foreach(f)
+  override def foreach[U](f: A => U): Unit = self.foreach(f)
   override def isEmpty: Boolean = self.isEmpty
   override def nonEmpty: Boolean = self.nonEmpty
   override def size: Int = self.size