fixup: try without --prefix

Author: frasertweedale

.github/workflows/haskell-ci.yml

@@ -1246,7 +1246,7 @@ jobs:
             (curl -L https://notmuchmail.org/releases/notmuch-$NOTMUCHVER.tar.gz | tar xz --wildcards --strip-components=1 -C /tmp/notmuch) \
             || (curl -L https://notmuchmail.org/releases/notmuch-$NOTMUCHVER.tar.xz | tar xJ --wildcards --strip-components=1 -C /tmp/notmuch)
           fi
-          (cd /tmp/notmuch && ./configure --prefix=/usr --without-emacs --without-ruby && make)
+          (cd /tmp/notmuch && ./configure --without-emacs --without-ruby && make)
       - name: install libnotmuch
         run: |
           (cd /tmp/notmuch && make install)