ci: chmod go-w ~/.cache before pkg commands (sr.ht cache is group-writable)

ober

a55eaf88eecaac0ddcc09e5aab3e84d34a8b8de0

diff --git a/.builds/ci.yml b/.builds/ci.yml
index c1445a2..fe6efe6 100644
--- a/.builds/ci.yml
+++ b/.builds/ci.yml
@@ -31,6 +31,7 @@ tasks:
 - package: |
     cd jerboa-sed
     J="$HOME/jerboa/dist/jerboa"
+    chmod -R go-w "$HOME/.cache"
     "$J" pkg verify
     "$J" pkg policy
     "$J" pkg build