fix format string in dap-debug-edit-template

[krfantasy]

In e3c2e50, prin1-to-string was replaced with a format string %s, which makes dap-debug-edit-template to produce string object without quoting,

(dap-register-debug-template
  "cpptools::Run Configuration"
  (list :type cppdbg
        :request launch  ;should be a string with quoting "launch", same as below
        :name cpptools::Run Configuration
        :MIMode gdb
        :program ${workspaceFolder}/ replace with your binary
        :cwd ${workspaceFolder}))

In order to replace prin1-to-string, it should use %S(using prin1) instead of %s(using princ).¹

Footnotes

1. https://www.gnu.org/software/emacs/manual/html_node/elisp/Formatting-Strings.html ↩