update graphics/nsxiv to v31

diff from maintainer Thim Cederlund, thanks!  tweak to post-install by me.
Changelog: https://codeberg.org/nsxiv/nsxiv/src/branch/master/etc/CHANGELOG.md

graphics/nsxiv/Makefile

@@ -2,7 +2,7 @@ COMMENT =	neo simple X Image Viewer
 
 GH_PROJECT =	nsxiv
 GH_ACCOUNT =	nsxiv
-GH_TAGNAME =	v30
+GH_TAGNAME =	v31
 
 CATEGORIES =	graphics x11
 
@@ -47,7 +47,7 @@ FAKE_TARGET =	install-all
 NO_TEST =	Yes
 
 post-patch:
-	${SUBST_CMD} ${WRKSRC}/nsxiv.1
+	${SUBST_CMD} ${WRKSRC}/etc/nsxiv.1
 
 # Git errors break version.h build; this makes it fall back to a
 # hardcoded value
@@ -55,8 +55,6 @@ pre-build:
 	ln -sf /usr/bin/true ${WRKDIR}/bin/git
 
 post-install:
-	${INSTALL_DATA_DIR} ${PREFIX}/share/applications
-	${INSTALL_DATA} ${WRKSRC}/nsxiv.desktop ${PREFIX}/share/applications
 	cd ${PREFIX}/bin && ln -s nsxiv sxiv
 
 .include <bsd.port.mk>

graphics/nsxiv/distinfo

@@ -1,2 +1,2 @@
-SHA256 (nsxiv-30.tar.gz) = TmAIxlynGlHVndfqfPDrSFctniB6dA9z8o58h35DTSs=
-SIZE (nsxiv-30.tar.gz) = 65642
+SHA256 (nsxiv-31.tar.gz) = v4ZS3Tkco7eHzxx/8s/aOag2ROITr0eAVTCfllVcJBs=
+SIZE (nsxiv-31.tar.gz) = 73821

graphics/nsxiv/patches/patch-etc-nsxiv_1

@@ -1,8 +1,8 @@
 Corrects the path of keysymdef.h.
 
 Index: nsxiv.1
---- nsxiv.1.orig
-+++ nsxiv.1
+--- etc/nsxiv.1.orig
++++ etc/nsxiv.1
 @@ -499,7 +499,7 @@ By default nsxiv(1) will send one image per-line to st
  
  The key combo argument has the following form: "[C-][M-][S-]KEY",