use correct inputs in NotifyFinish

[SeverinDiederichs]

We noticed incomplete communication calls on JUWELS by the following error:

[1630593559.537108] [jwb0097:21399:0]          mpool.c:43   UCX  WARN  object 0x1a214d00 was not returned to mpool ucp_requests
[1630593559.537689] [jwb0097:21396:0]          mpool.c:43   UCX  WARN  object 0x19786d00 was not returned to mpool ucp_requests
[1630593559.539651] [jwb0097:21398:0]          mpool.c:43   UCX  WARN  object 0x19d59980 was not returned to mpool ucp_requests
[1630593559.538533] [jwb0097:21397:0]          mpool.c:43   UCX  WARN  object 0x194ddd00 was not returned to mpool ucp_requests

This was caused by incorrect inputs into NotifyFinish, which was called via NotifyFinish(true);, but should have been NotifyFinish(0 ,true);, because the finishing of the ghost particle send must be on box 0. (The box parameter was simply missing).

This PR fixes the problem and removes the error.

• Small enough (< few 100s of lines), otherwise it should probably be split into smaller PRs
• Tested (describe the tests in the PR description)
• Runs on GPU (basic: the code compiles and run well with the new module)
• Contains an automated test (checksum and/or comparison with theory)
• Documented: all elements (classes and their members, functions, namespaces, etc.) are documented
• Constified (All that can be const is const)
• Code is clean (no unwanted comments, )
• Style and code conventions are respected at the bottom of https://github.com/Hi-PACE/hipace
• Proper label and GitHub project, if applicable