docs: fix grammatical error in Buffer Map API documentation

[Navadeep0007]

Remove redundant word 'pointer' in xrt::bo::map() description.

Fixes #8796

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[gbuildx]

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[Navadeep0007]

Hi @gbuildx, I have fixed the DCO issue.
The authorize check is failing because I am not a collaborator.
Could you please approve the workflow or add the build label?
Thanks!

[gbuildx]

⚠️ Authorization Failed

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[stsoe]

@Navadeep0007 I am not following what this change is changing? Is it adding a new file? What file is changed?