Update entrypoint.sh.tmpl

The old command would place "X_FRAME_OPTIONS_ALLOW_FROM" outside of the square brackets

```
protected $allowedChildSrcDomains = [];
                'example.org',
```

The changes to the sed command places them inline, also allowing for multiple domains to be set

```
protected $allowedChildSrcDomains = [ 'example.org', 'exampletwo.org' ];
```

entrypoint.sh.tmpl

@@ -30,7 +30,7 @@ echo "Giving the db container some time to come up"; sleep 20
 
 {{ if eq (env "X_FRAME_OPTIONS_ENABLED") "1" }}
 if ! [[ $(grep {{ env "X_FRAME_OPTIONS_ALLOW_FROM" }} lib/public/AppFramework/Http/ContentSecurityPolicy.php) ]]; then
-    sed -i "91 a\\\t\t'{{ env "X_FRAME_OPTIONS_ALLOW_FROM" }}', " lib/public/AppFramework/Http/ContentSecurityPolicy.php
+  sed -i "s|protected \$allowedChildSrcDomains = \[\];|protected \$allowedChildSrcDomains = [ {{ env \"X_FRAME_OPTIONS_ALLOW_FROM\" }} ];|" lib/public/AppFramework/Http/ContentSecurityPolicy.php
 fi
 {{ end }}