srht: Remove NetBSD build

This isn't officially supported (yet?), and it's currently broken.

It doesn't include ssl certificates,
and I can't see a way to add them or disable verification before it attempts to clone the git repo.

Ironically:

[ci skip]

.builds/netbsd.yml

@@ -1,23 +0,0 @@
-image: netbsd/latest
-packages:
-  - ncurses
-  - gettext
-  - tcl-expect
-  - cmake
-  - gmake
-  - pcre2
-tasks:
-  - build: |
-          git -c http.sslVerify=false clone  https://git.sr.ht/~faho/fish
-          cd fish
-          mkdir build || :
-          cd build
-          cmake .. \
-          -DCMAKE_INSTALL_PREFIX=/usr \
-          -DCMAKE_INSTALL_DATADIR=share \
-          -DCMAKE_INSTALL_DOCDIR=share/doc/fish \
-          -DCMAKE_INSTALL_SYSCONFDIR=/etc
-          gmake -j2
-  - test: |
-          cd fish/build
-          gmake test SHOW_INTERACTIVE_LOG=1