Bump cakephp/cakephp from 3.4.7 to 3.5.18 in /cake3/rd_cake

Bumps [cakephp/cakephp](https://github.com/cakephp/cakephp) from 3.4.7 to 3.5.18.
- [Release notes](https://github.com/cakephp/cakephp/releases)
- [Commits](cakephp/cakephp@3.4.7...3.5.18)

Signed-off-by: dependabot[bot] <[email protected]>

Author: dependabot[bot]

cake3/rd_cake/composer.json

@@ -6,7 +6,7 @@
     "license": "MIT",
     "require": {
         "php": ">=5.5.9",
-        "cakephp/cakephp": "3.4.*",
+        "cakephp/cakephp": "3.5.*",
         "mobiledetect/mobiledetectlib": "2.*",
         "cakephp/migrations": "~1.0",
         "cakephp/plugin-installer": "*",