FIXME(47184) update fixmes to point to issues specific to them

Author: nivkner

src/librustc_mir/build/matches/test.rs

@@ -347,7 +347,7 @@ impl<'a, 'gcx, 'tcx> Builder<'a, 'gcx, 'tcx> {
                             span: test.span,
                             ty: mty,
 
-                            // FIXME(#47184): This constant comes from user
+                            // FIXME(#54571): This constant comes from user
                             // input (a constant in a pattern).  Are
                             // there forms where users can add type
                             // annotations here?  For example, an

src/librustc_mir/hair/pattern/mod.rs

@@ -83,7 +83,7 @@ impl<'tcx> PatternTypeProjections<'tcx> {
     }
 
     pub(crate) fn ref_binding(&self) -> Self {
-        // FIXME(#47184): ignore for now
+        // FIXME(#55401): ignore for now
         PatternTypeProjections { contents: vec![] }
     }