Correct acronym for (G)OSPA in documentation

[codecov[bot]]

Codecov Report

Base: 94.81% // Head: 94.81% // No change to project coverage :thumbsup:

Coverage data is based on head (0512c86) compared to base (b8984aa). Patch has no changes to coverable lines.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #741 +/- ## ======================================= Coverage 94.81% 94.81% ======================================= Files 169 169 Lines 8221 8221 Branches 1216 1216 ======================================= Hits 7795 7795 Misses 316 316 Partials 110 110 ``` | Flag | Coverage Δ | | |---|---|---| | integration | `69.11% <ø> (ø)` | | | unittests | `92.65% <ø> (ø)` | | Flags with carried forward coverage won't be shown. [Click here](https://docs.codecov.io/docs/carryforward-flags?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dstl#carryforward-flags-in-the-pull-request-comment) to find out more. | [Impacted Files](https://codecov.io/gh/dstl/Stone-Soup/pull/741?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dstl) | Coverage Δ | | |---|---|---| | [stonesoup/metricgenerator/ospametric.py](https://codecov.io/gh/dstl/Stone-Soup/pull/741/diff?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dstl#diff-c3RvbmVzb3VwL21ldHJpY2dlbmVyYXRvci9vc3BhbWV0cmljLnB5) | `86.39% <ø> (ø)` | | Help us with your feedback. Take ten seconds to tell us [how you rate us](https://about.codecov.io/nps?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dstl). Have a feature suggestion? [Share it here.](https://app.codecov.io/gh/feedback/?utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=dstl)

:umbrella: View full report at Codecov.
:loudspeaker: Do you have feedback about the report comment? Let us know in this issue.