fix(command-development): correct grep pattern in testing-strategies

The grep command for verifying bash command syntax was searching for
the escaped pattern `!\`` instead of the actual syntax `!``.

🤖 Generated with [Claude Code](https://claude.com/claude-code)

Co-Authored-By: Claude <noreply@anthropic.com>

Author: sjnims

plugins/plugin-dev/skills/command-development/references/testing-strategies.md

@@ -677,7 +677,7 @@ echo "Test: \$1 and \$2" > .claude/commands/test-args.md
 grep "allowed-tools" .claude/commands/my-command.md
 
 # Verify command syntax
-grep '!\`' .claude/commands/my-command.md
+grep '!`' .claude/commands/my-command.md
 
 # Test command manually
 date