Update lectures/polars.md

Co-authored-by: Humphrey Yang <39026988+HumphreyYang@users.noreply.github.com>

Author: mmcky

lectures/polars.md

@@ -30,9 +30,7 @@ In addition to what's in Anaconda, this lecture will need the following librarie
 ```{code-cell} ipython3
 :tags: [hide-output]
 
-!pip install --upgrade polars
-!pip install --upgrade wbgapi
-!pip install --upgrade yfinance
+!pip install --upgrade polars wbgapi yfinance
 ```
 
 ## Overview