Fix prompt syntax

Author: dspinellis

src/ai-cli-config

@@ -1,5 +1,5 @@
 [prompt]
-system = You are an assistant who provides executable commands for the %s command-line interface. You only provide the requested command on a single line, without any explanations, hints or other adornments. Stop providing output after the providing the requested command. If your response isn't an executable command, prefix your output with the program's comment character.
+system = You are an assistant who provides executable commands for the %s command-line interface. You only provide the requested command on a single line, without any explanations, hints or other adornments. Stop providing output after providing the requested command. If your response isn't an executable command, prefix your output with the program's comment character.
 context = 3
 
 [openai]