gnu: Fix various synopsis and description issues.

* gnu/packages/admin.scm (greetd-pam-mount)[synopsis]: Base synopsis on
  pam-mount synopsis.
  [description]: Use two spaces consistently.
  (greetd)[synopsis]: Begin sentence with upper-case.
* gnu/packages/xdisorg.scm (wlsunset)[description]: Fix spelling and case of
  wlsunsest.
* gnu/packages/mail.scm (libpst): Add synopsis.
* gnu/packages/networking.scm (librecast)[synopsis]: Update synopsis.
  (lcrq)[description]: Use two spaces after sentences.

gnu/packages/admin.scm

@@ -5214,7 +5214,7 @@ it won't take longer to install 15 machines than it would to install just 2.")
     (native-inputs
      `(("linux-pam" ,linux-pam)
        ("scdoc" ,scdoc)))
-    (synopsis "minimal and flexible login manager daemon")
+    (synopsis "Minimal and flexible login manager daemon")
     (description
      "greetd is a minimal and flexible login manager daemon
 that makes no assumptions about what you want to launch.
@@ -5242,7 +5242,7 @@ then it can be a greeter.")
                   "#define CONFIGFILE \"/etc/security/greetd_pam_mount.conf.xml\"\n")
                  (("pam_mount_config") "greetd_pam_mount_config")
                  (("pam_mount_system_authtok") "greetd_pam_mount_system_authtok"))))))))
-    (synopsis "pam-mount specifically compiled for use with greetd")
+    (synopsis "PAM module to mount volumes for a user session (greetd variant)")
     (description
      "Pam-mount is a PAM module that can mount volumes when a user logs in.
 It supports mounting local filesystems of any kind the normal mount utility

gnu/packages/mail.scm

@@ -4533,7 +4533,7 @@ undelete email messages from Outlook Express .dbx files.")
     (native-inputs
      (list pkg-config))
     (home-page "https://www.five-ten-sg.com/libpst/")
-    (synopsis "")
+    (synopsis "Tools to process Outlook email archives")
     (description "The Libpst utilities include @code{readpst} which can
 convert email messages to both mbox and MH mailbox formats, @code{pst2ldif}
 which can convert the contacts to @code{.ldif} format for import into LDAP

gnu/packages/networking.scm

@@ -524,7 +524,7 @@ GLib-based library, libnice, as well as GStreamer elements to use it.")
                       (delete-file "./test/0000-0039.c")
                       (delete-file "./test/0000-0040.c"))))))
     (inputs (list libsodium lcrq))
-    (synopsis "librecast IPv6 multicast library")
+    (synopsis "IPv6 multicast library")
     (description "Librecast is a C library which supports IPv6 multicast
 networking.")
     (home-page "https://librecast.net/librecast.html")

gnu/packages/xdisorg.scm

@@ -3163,7 +3163,7 @@ MouseKeys-acceleration management.")
     (synopsis "Day/night gamma adjustments for Wayland compositors")
     (home-page "https://sr.ht/~kennylevinsen/wlsunset/")
     (description
-     "wlunset adjusts gamma based on day-night cycles on Wayland compositors
+     "Wlsunset adjusts gamma based on day-night cycles on Wayland compositors
 that support @samp{wlr-gamma-control-unstable-v1}.  It is also known as a blue
 light filter or night light.")
     (license license:expat)))