linux-pam: remove broken musl pam_exec patch

it looks like this build wasn't tested with musl-libc after upgrading to
1.5.1, and has been broken in this configuration since, as the removed
patch does not apply cleanly. the good news is it's been fixed upstream,
rendering it unnecessary.

pkgs/os-specific/linux/pam/default.nix

@@ -20,9 +20,6 @@ stdenv.mkDerivation rec {
       url = "https://git.alpinelinux.org/aports/plain/main/linux-pam/libpam-fix-build-with-eglibc-2.16.patch?id=05a62bda8ec255d7049a2bd4cf0fdc4b32bdb2cc";
       sha256 = "1ib6shhvgzinjsc603k2x1lxh9dic6qq449fnk110gc359m23j81";
     })
-    # From adelie's package repo, using local copy since it seems to be currently offline.
-    # (we previously used similar patch from void, but stopped working with update to 1.3.1)
-    ./musl-fix-pam_exec.patch
   ];
 
   outputs = [ "out" "doc" "man" /* "modules" */ ];

pkgs/os-specific/linux/pam/musl-fix-pam_exec.patch

@@ -1,33 +0,0 @@
---- ./modules/pam_exec/pam_exec.c.orig
-+++ ./modules/pam_exec/pam_exec.c
-@@ -103,11 +103,14 @@
-   int optargc;
-   const char *logfile = NULL;
-   const char *authtok = NULL;
-+  char authtok_buf[PAM_MAX_RESP_SIZE+1];
-+
-   pid_t pid;
-   int fds[2];
-   int stdout_fds[2];
-   FILE *stdout_file = NULL;
- 
-+  memset(authtok_buf, 0, sizeof(authtok_buf));
-   if (argc < 1) {
-     pam_syslog (pamh, LOG_ERR,
- 		"This module needs at least one argument");
-@@ -180,12 +183,12 @@
- 	      if (resp)
- 		{
- 		  pam_set_item (pamh, PAM_AUTHTOK, resp);
--		  authtok = strndupa (resp, PAM_MAX_RESP_SIZE);
-+		  authtok = strncpy(authtok_buf, resp, sizeof(authtok_buf));
- 		  _pam_drop (resp);
- 		}
- 	    }
- 	  else
--	    authtok = strndupa (void_pass, PAM_MAX_RESP_SIZE);
-+	    authtok = strncpy(authtok_buf, void_pass, sizeof(authtok_buf));
- 
- 	  if (pipe(fds) != 0)
- 	    {
-