Add changeset for space migration (#10727)

laurkim · web-flow · commit 179b481d745c · 2023-09-27T14:39:03.000-04:00
### WHY are these changes introduced? Forgot to add a changeset when I merged [this](#10585) into `next`.
diff --git a/.changeset/lemon-bees-confess.md b/.changeset/lemon-bees-confess.md
@@ -0,0 +1,5 @@
+---
+'@shopify/polaris': minor
+---
+
+Migrated `space` custom properties from v11 to v12

-Original file line number
+Diff line change
@@ @@ -0,0 +1,5 @@ @@
 +---
 +'@shopify/polaris': minor
 +---
++
 +Migrated `space` custom properties from v11 to v12