Merge #6300

6300: Updating APEX default version to v2.6.3 r=hkaiser a=khuck

Updating APEX default version to v2.6.3

## Proposed Changes

- see changelist here: https://github.com/UO-OACISS/apex/releases/tag/v2.6.3

## Any background context you want to provide?

## Checklist

Not all points below apply to all pull requests.

- [ ] I have added a new feature and have added tests to go along with it.
- [ ] I have fixed a bug and have added a regression test.
- [ ] I have added a test using random numbers; I have made sure it uses a seed, and that random numbers generated are valid inputs for the tests.
- [x]  I tested the change :)


Co-authored-by: Kevin Huck <khuck@cs.uoregon.edu>

CMakeLists.txt

@@ -944,7 +944,7 @@ if(HPX_WITH_APEX)
     "Do not update code from remote APEX repository." OFF CATEGORY "Profiling"
   )
   hpx_option(
-    HPX_WITH_APEX_TAG STRING "APEX repository tag or branch" "v2.6.2"
+    HPX_WITH_APEX_TAG STRING "APEX repository tag or branch" "v2.6.3"
     CATEGORY "Profiling"
   )
 endif()