Fix invalid link (modular#2112)

Fixes modular#2107

Signed-off-by: Xida Ren (Cedar) <[email protected]>

Author: renxida

README.md

@@ -40,7 +40,7 @@ or the standalone Mojo SDK:
 - [Get the Mojo SDK](https://docs.modular.com/mojo/manual/get-started/)
 
 Then follow the docs to [write your first Mojo
-program](https://https://docs.modular.com/mojo/manual/get-started/hello-world).
+program](https://docs.modular.com/mojo/manual/get-started/hello-world).
 
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