translation: Update chap_tree/summary.md

[steventimes]

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[steventimes]

I have changed some wording, and for line 37, since I do not know c++, I am not sure whether to use "function" or "method".

[yuelinxin]

Functions defined in an object in cpp is usually referred as a “method”, this follows the terminology commonly accepted in object-oriented programming.

[yuelinxin]

Great work! Please consider my comment on the title and also the function terminology.

[yuelinxin]

we have fixed this title throughout this book so no need to change this

[steventimes]

I have updated the file with the changed title, and named back to "method". Thank you

[yuelinxin]

Great work, thank you!