feat(smartlog): switch from ⊘ to ◌ for synthetic omitted-commit nodes

This seems like a strictly more understandable icon. (Originally suggested by @martinvonz for jj.)

Author: arxanas

git-branchless-lib/src/core/formatting.rs

@@ -202,7 +202,7 @@ impl Glyphs {
             commit_visible_head: "●",
             commit_obsolete: "✕",
             commit_obsolete_head: "⦻",
-            commit_omitted: "⊘",
+            commit_omitted: "◌",
             commit_merge: "↓",
             commit_main: "◇",
             commit_main_head: "◆",