fix(prompts): avoid %20 being treated as special sequence when relacing dirname (#1525)

* Wrap source.cwd in function

tackles ticket #1524

* [pre-commit.ci] auto fixes from pre-commit.com hooks

for more information, see https://pre-commit.ci

* CWD function handed directly #1524

Assumption that source.cwd function will not accept any arguments
in the future as it currently doesn't allows simplification

---------

Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>

Author: Tlunch

lua/CopilotChat/prompts.lua

@@ -343,7 +343,7 @@ function M.resolve_prompt(prompt, config)
 
     config.system_prompt = config.system_prompt:gsub('{OS_NAME}', vim.uv.os_uname().sysname)
     config.system_prompt = config.system_prompt:gsub('{LANGUAGE}', config.language)
-    config.system_prompt = config.system_prompt:gsub('{DIR}', source.cwd())
+    config.system_prompt = config.system_prompt:gsub('{DIR}', source.cwd)
   end
 
   return config, prompt