Update to Ruby 3.1.5 and 3.2.4

This fixes a number of CVEs a bugs:

* https://www.ruby-lang.org/en/news/2024/04/23/ruby-3-1-5-released/
* https://www.ruby-lang.org/en/news/2024/04/23/ruby-3-2-4-released/

This will also enable us to update to Puma 6.4.2
since https://bugs.ruby-lang.org/issues/19837 has been resolved
in Ruby 3.1.5.

This drops the `fix-ruby-xfree-for-libxml2.patch` patch for Ruby 3.1.5
since the change has been merged upstream.

patches/ruby/3.1/fix-ruby-xfree-for-libxml2.patch

@@ -1,23 +0,0 @@
-diff --git a/gc.c b/gc.c
-index 030a4627bd..1c96f6401f 100644
---- a/gc.c
-+++ b/gc.c
-@@ -11763,8 +11763,16 @@ ruby_xrealloc2_body(void *ptr, size_t n, size_t size)
- void
- ruby_sized_xfree(void *x, size_t size)
- {
--    if (x) {
--	objspace_xfree(&rb_objspace, x, size);
-+    if (LIKELY(x)) {
-+        /* It's possible for a C extension's pthread destructor function set by pthread_key_create
-+         * to be called after ruby_vm_destruct and attempt to free memory. Fall back to mimfree in
-+         * that case. */
-+        if (LIKELY(GET_VM())) {
-+            objspace_xfree(&rb_objspace, x, size);
-+        }
-+        else {
-+            ruby_mimfree(x);
-+        }
-     }
- }
-