chore: remove pointless root release configuration

The root '.' release was just bumping a version number and updating
a changelog for commits that don't belong to any package. In a
monorepo, each package should have its own releases. There's no
meaningful 'root' package to release.

Author: bowlofarugula

.release-please-manifest.json

@@ -1,5 +1,4 @@
 {
-  ".": "0.12.0",
   "cmd/ftl": "0.11.0",
   "sdk/go": "0.11.0",
   "sdk/rust": "0.13.0",

release-please-config.json

@@ -81,13 +81,6 @@
     }
   ],
   "packages": {
-    ".": {
-      "release-type": "simple",
-      "component": "",
-      "changelog-path": "CHANGELOG.md",
-      "include-component-in-tag": false,
-      "package-name": "ftl"
-    },
     "cmd/ftl": {
       "release-type": "go",
       "component": "cli",