translation: Refine the first paragraph of Time Complexity (#1471)

* Update time_complexity.md

Update first paragraph to avoid confusion between time complexity and run time

* Update time_complexity.md

Refine the first paragraph to keep the definition of time complexity

* Update time_complexity.md

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Co-authored-by: Yudong Jin <krahets@163.com>

en/docs/chapter_computational_complexity/time_complexity.md

@@ -1,6 +1,6 @@
 # Time complexity
 
-Time complexity is a concept used to measure how the run time of an algorithm increases with the size of the input data. Understanding time complexity is crucial for accurately assessing the efficiency of an algorithm.
+The runtime can intuitively assess the efficiency of an algorithm. How can we accurately estimate the runtime of a piece of an algorithm?
 
 1. **Determining the Running Platform**: This includes hardware configuration, programming language, system environment, etc., all of which can affect the efficiency of code execution.
 2. **Evaluating the Run Time for Various Computational Operations**: For instance, an addition operation `+` might take 1 ns, a multiplication operation `*` might take 10 ns, a print operation `print()` might take 5 ns, etc.