docs: updating the intentation for previous install method

Co-authored-by: Xiaotian Gu <[email protected]>

Author: Darsh0307

doc/getting-started.md

@@ -72,7 +72,7 @@ Option 2:- To incorporate the Uno Toolkit into an existing application, you must
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-#### Previous Installation Method
+## Previous Installation Method
 
 If your application is based on the older solution template that includes a shared project (.shproj), follow these steps: