fix(elisp): add lexical-binding comment to all files to suppress new Emacs 31 warnings

I've set `lexical-binding` to `nil` in all Emacs Lisp files to suppress
the warnings introduced in Emacs 31 requiring all elisp files to have a
`lexical-binding` comment.

This retains the default behavior of dynamic binding when no
`lexical-binding` comment is present. With it set to `t` across the
board, various things break, and fixing those is a task for another day.

modules/tools/siren-docker.el

@@ -1,4 +1,4 @@
-;;; siren-docker.el --- jimeh's Emacs Siren: docker configuration.
+;;; siren-docker.el --- jimeh's Emacs Siren: docker configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/tools/siren-helm-make.el

@@ -1,4 +1,4 @@
-;;; siren-helm-make.el --- jimeh's Emacs Siren: helm-make configuration.
+;;; siren-helm-make.el --- jimeh's Emacs Siren: helm-make configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/tools/siren-httprepl.el

@@ -1,4 +1,4 @@
-;;; siren-httprepl.el --- jimeh's Emacs Siren: httprepl configuration.
+;;; siren-httprepl.el --- jimeh's Emacs Siren: httprepl configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/tools/siren-kubernetes.el

@@ -1,4 +1,4 @@
-;;; siren-kubernetes.el --- jimeh's Emacs Siren: kubernetes configuration.
+;;; siren-kubernetes.el --- jimeh's Emacs Siren: kubernetes configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/tools/siren-makefile-executor.el

@@ -1,4 +1,4 @@
-;;; siren-makefile-executor.el --- jimeh's Emacs Siren: makefile-executor configuration.
+;;; siren-makefile-executor.el --- jimeh's Emacs Siren: makefile-executor configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/tools/siren-pandoc.el

@@ -1,4 +1,4 @@
-;;; siren-pandoc.el --- jimeh's Emacs Siren: pandoc-mode configuration.
+;;; siren-pandoc.el --- jimeh's Emacs Siren: pandoc-mode configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary:
 

modules/tools/siren-restclient.el

@@ -1,4 +1,4 @@
-;;; siren-restclient.el --- jimeh's Emacs Siren: restclient configuration.
+;;; siren-restclient.el --- jimeh's Emacs Siren: restclient configuration.  -*- lexical-binding: nil; -*-
 
 ;;; Commentary: