Remove the catta submodule.

[meshlink] / catta

diff --git a/catta b/catta
deleted file mode 160000 (submodule)
index 070b95d..0000000
--- a/catta
+++ /dev/null
@@ -1 +0,0 @@
-Subproject commit 070b95d769cbcbdf0113437a0db92777765474ea