Update grammar of internals.rst

Some changes that I think help the docs read easier.
minor #1220 Update grammar of internals.rst (steveoliver)

This PR was merged into the master branch.

Discussion
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Update grammar of internals.rst

Fabien,

Here are some changes that I think help the Internals docs page read easier.

Commits
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6c80601 Update grammar of internals.rst