Comment style fixes

Co-Authored-By: matthewjasper <mjjasper1@gmail.com>

src/librustc_mir/build/expr/as_temp.rs

@@ -75,8 +75,8 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                 },
             );
 
-            // In constants, temp_lifetime is None for temporaries that live for the
-            // 'static lifetime. Thus we do not drop these temporaries and simply leak them.
+            // In constants, `temp_lifetime` is `None` for temporaries that live for the
+            // `'static` lifetime. Thus we do not drop these temporaries and simply leak them.
             // This is equivalent to what `let x = &foo();` does in functions. The temporary
             // is lifted to their surrounding scope. In a function that means the temporary lives
             // until just before the function returns. In constants that means it outlives the

src/librustc_mir/build/scope.rs

@@ -900,7 +900,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
     /// * The variable must be in that scope.
     /// * The variable must be at the top of that scope: it's the next thing
     ///   scheduled to drop.
-    /// * The drop must be of DropKind::Storage.
+    /// * The drop must be of `DropKind::Storage`.
     ///
     /// This is used for the boolean holding the result of the match guard. We
     /// do this because: