Update README.md

Author: actions-user

2021/README.md

@@ -22,7 +22,7 @@
 | [Day 14](Day_14) | `4ms` | :x: |
 | [Day 15](Day_15) | `420ms` | :x: |
 | [Day 16](Day_16) | `3ms` | :x: |
-| [Day 17](Day_17) | :x: | :x: |
+| [Day 17](Day_17) | `678μs` | :x: |
 | [Day 18](Day_18) | :x: | :x: |
 | [Day 19](Day_19) | :x: | :x: |
 | [Day 20](Day_20) | :x: | :x: |