Don't store region in CapturedPlace

compiler/rustc_middle/src/ty/closure.rs

@@ -88,9 +88,6 @@ pub struct CapturedPlace<'tcx> {
 
     /// Represents if `place` can be mutated or not.
     pub mutability: hir::Mutability,
-
-    /// Region of the resulting reference if the upvar is captured by ref.
-    pub region: Option<ty::Region<'tcx>>,
 }
 
 impl<'tcx> CapturedPlace<'tcx> {