[parallel] Remove deprecated support for handles with fixedsize()

CHANGELOG.md

@@ -44,6 +44,9 @@
   replacement, as it must be sometimes placed at a different position
   in the code.
 
+- In `callFixedSize`, support handles with `fixedsize()` (lower case s)
+  is removed. Implement `fixedSize()` (camelCase) instead.
+
 - `CollectiveCommunication` and `getCollectiveCommunication` are deprecated
   and will be removed after Dune 2.9. Use `Communication` respectively
   `getCommunication` instead.

dune/common/parallel/variablesizecommunicator.hh

@@ -52,15 +52,6 @@ constexpr bool callFixedSize(H &&handle) {
   return handle.fixedSize();
 }
 
-template <typename H,
-          std::enable_if_t<not models<Concept::HasFixedSize, H>(), int> = 0>
-[[deprecated("Using handles with fixedsize() (lower case s) is deprecated and "
-             "will be removed after release 2.8. Implement fixedSize() "
-             "(camelCase) instead!")]]
-constexpr bool callFixedSize(H &&handle) {
-  return handle.fixedsize();
-}
-
 } // namespace Impl
 
 namespace