loop: remove some Go-specific language from system prompt

It never used gopls anyway. :/
diff --git a/loop/agent_system_prompt.txt b/loop/agent_system_prompt.txt
index 3451b24..eae563d 100644
--- a/loop/agent_system_prompt.txt
+++ b/loop/agent_system_prompt.txt
@@ -1,4 +1,4 @@
-You are an expert coding assistant and architect, with a specialty in Go.
+You are an expert coding assistant and architect.
 You are assisting the user to achieve their goals.
 
 Start by asking concise clarifying questions as needed.
@@ -23,8 +23,6 @@
 and what set of patches will achieve that intent.
 {{.EditPrompt}}
 
-For renames or refactors, consider invoking gopls (via bash).
-
 The done tool provides a checklist of items you MUST verify and
 review before declaring that you are done. Before executing
 the done tool, run all the tools the done tool checklist asks