Remove example extension (#14376)

hello/commands/fs/grep-code.toml

@@ -1,6 +0,0 @@
-prompt = """
-Please summarize the findings for the pattern `{{args}}`.
-
-Search Results:
-!{grep -r {{args}} .}
-"""

hello/gemini-extension.json

@@ -1,4 +0,0 @@
-{
-  "name": "custom-commands",
-  "version": "1.0.0"
-}