fix: remove redundant tb-clear! that caused full-screen flicker on every keystroke

ober

4782cb8d4b1b79dc48892f6ba791baf4fb6f4b99

diff --git a/signal/tui/main.ss b/signal/tui/main.ss
index 51c3bc6..45224ac 100644
--- a/signal/tui/main.ss
+++ b/signal/tui/main.ss
@@ -2581,8 +2581,6 @@
            [details-x (- w details-w)]
            [body-h (max 4 (- h 4))]
            [composer-y (- h 3)])
-      (tb-set-clear-attrs! (fg) (bg))
-      (tb-clear!)
       (fill-rect! 0 0 w h (fg) (bg))
 
       (cond