Update 05_introduction_to_causaltune.md: adding up-to-date documentation link

Hello, adding up-to-date documentation link for CausalTune, could you please approve and merge? Thank you

Signed-off-by: AlxdrPolyakov <[email protected]>

Author: AlxdrPolyakov

_learn/05_introduction_to_causaltune.md

@@ -15,7 +15,7 @@ summary: >-
   
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-  <a href="https://www.pywhy.org/causaltune/">CausalTune Documentation</a>
+  <a href="https://causaltune.readthedocs.io/en/latest/">CausalTune Documentation</a>
   <br>
   <a href="https://github.com/py-why/causaltune">CausalTune GitHub Repository</a>