Trailing white space and feature name

Removed trailing whitespace to pass travis builds, renamed feature to vec_remove_item.

Author: madseagames

src/libcollections/vec.rs

@@ -1296,8 +1296,8 @@ impl<T: PartialEq> Vec<T> {
     pub fn dedup(&mut self) {
         self.dedup_by(|a, b| a == b)
     }
-    
-    #[unstable(feature = "remove_from", reason = "recently added", issue = "38143")]
+
+    #[unstable(feature = "vec_remove_item", reason = "recently added", issue = "38143")]
     pub fn remove_item(&mut self, item: &T) -> Option<usize> {
         let pos = match self.iter().position(|x| *x == *item) {
             Some(x) => x,