Update marketing copy

[WildDanDan]

This PR fixes a grammatical error that's immediately visible on the Memray landing page.

[codecov-commenter]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

Project coverage is 92.32%. Comparing base (51aa84e) to head (4783644). Report is 143 commits behind head on main.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #509 +/- ## ========================================== - Coverage 92.37% 92.32% -0.06% ========================================== Files 91 91 Lines 11270 11270 Branches 1571 1571 ========================================== - Hits 10411 10405 -6 - Misses 854 860 +6 Partials 5 5 ``` | [Flag](https://app.codecov.io/gh/bloomberg/memray/pull/509/flags?src=pr&el=flags&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bloomberg) | Coverage Δ | | |---|---|---| | [cpp](https://app.codecov.io/gh/bloomberg/memray/pull/509/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bloomberg) | `85.66% <ø> (-0.17%)` | :arrow_down: | | [python_and_cython](https://app.codecov.io/gh/bloomberg/memray/pull/509/flags?src=pr&el=flag&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=bloomberg) | `95.53% <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=bloomberg#carryforward-flags-in-the-pull-request-comment) to find out more.

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[godlygeek]

Whoops, thanks @WildDanDan!