[3.9] [doc] Fix typo in idle.rst (GH-27903)

[miss-islington]

intially -> initially
(cherry picked from commit 0e8695e)

Co-authored-by: Ikko Ashimine [email protected]

[miss-islington]

@eltociear and @ambv: Status check is done, and it's a failure ❌ .

[miss-islington]

@eltociear and @ambv: Status check is done, and it's a failure ❌ .

[miss-islington]

@eltociear and @ambv: Status check is done, and it's a success ✅ .

[miss-islington]

@eltociear and @ambv: Status check is done, and it's a success ✅ .

[miss-islington]

@eltociear and @ambv: Status check is done, and it's a success ✅ .

[miss-islington]

@eltociear and @ambv: Status check is done, and it's a success ✅ .

[miss-islington]

@eltociear and @ambv: Status check is done, and it's a success ✅ .

[miss-islington]

@eltociear and @ambv: Status check is done, and it's a success ❌ .