[niepce] Remove leftovers from libview

[Hubert Figuière <hub src gnome org>]

commit e033e012da203f60a4c5d4efd75cbb4381b02309
Author: Hubert Figuière <hub figuiere net>
Date:   Tue May 31 21:48:12 2022 -0400

    Remove leftovers from libview

 configure.ac                |   1 -
 src/ext/libview/Makefile.am |   8 ---
 src/ext/libview/header.cc   | 171 --------------------------------------------
 src/ext/libview/header.hh   |  63 ----------------
 4 files changed, 243 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index 6619f1a..a423790 100644
--- a/configure.ac
+++ b/configure.ac
@@ -156,7 +156,6 @@ data/themes/Makefile
 third_party/Makefile
 src/Makefile
 src/ext/Makefile
-src/ext/libview/Makefile
 src/fwk/Makefile
 src/fwk/base/Makefile
 src/fwk/utils/Makefile