Update path to generated HelloWorld source files.

Author: xiaojun-liu

docs/writing-reactors/a-first-reactor.mdx

@@ -60,7 +60,7 @@ The Lingua Franca tools assume that LF programs are put into a file with a `.lf`
         #####################################
         To run the generated program, use:
 
-            node ...path-to-project.../src-gen/Minimal/dist/Minimal.js
+            node ...path-to-project.../src-gen/HelloWorld/dist/HelloWorld.js
 
         #####################################
         ```
@@ -70,7 +70,7 @@ The Lingua Franca tools assume that LF programs are put into a file with a `.lf`
         #####################################
         To run the generated program, use:
 
-            python3 ...path-to-project.../src-gen/Minimal/Minimal.py
+            python3 ...path-to-project.../src-gen/HelloWorld/HelloWorld.py
 
         #####################################
         ```