hello-world.md: Change username to GitHub handle.

somyaraj · Balaji2198 · commit 0c113a94d0c2 · 2018-01-07T10:44:14.000+05:30
diff --git a/submit-a-pull-request/somyaraj/hello-world.md b/submit-a-pull-request/somyaraj/hello-world.md
@@ -1,2 +1,2 @@
 Hello world
-I am username. :tada:
+I am somyaraj. :tada:
