Update README.md

Update the latest released version.

README.md

@@ -10,7 +10,7 @@ SkyWalking: Large-Scale Distributed Systems Tracing Infrastructure, also known D
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 # News
 * sky-walking v3.0 iteration begins... The top 2 important features are: [`Update the trace-structure`](https://github.com/wu-sheng/sky-walking/issues/83) and [`Analyze trace, and bring metric/analytic/cause up`](https://github.com/wu-sheng/sky-walking/issues/84)