fix typo in oauth1.rst

[derenrich]

What kind of change does this PR introduce? (check at least one)

• [ ] Bugfix
• [ ] Feature
• [x] Code style update
• [ ] Refactor
• [x] Other, please describe:

typo fix in docs

Does this PR introduce a breaking change? (check one)

• [ ] Yes
• [x] No

If yes, please describe the impact and migration path for existing applications:

(If no, please delete the above question and this text message.)

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