fix: make branch as link field

erpnext/hr/doctype/salary_slip/salary_slip.json

@@ -195,7 +195,7 @@
    "columns": 0, 
    "fetch_from": "employee.branch", 
    "fieldname": "branch", 
-   "fieldtype": "Read Only", 
+   "fieldtype": "Link",
    "hidden": 0, 
    "ignore_user_permissions": 0, 
    "ignore_xss_filter": 0, 
@@ -208,11 +208,11 @@
    "no_copy": 0, 
    "oldfieldname": "branch", 
    "oldfieldtype": "Link", 
-   "options": "", 
+   "options": "Branch",
    "permlevel": 0, 
    "print_hide": 0, 
    "print_hide_if_no_value": 0, 
-   "read_only": 0, 
+   "read_only": 1,
    "remember_last_selected_value": 0, 
    "report_hide": 0, 
    "reqd": 0, 
@@ -1906,7 +1906,7 @@
  "issingle": 0, 
  "istable": 0, 
  "max_attachments": 0, 
- "modified": "2019-01-30 11:28:11.774739", 
+ "modified": "2019-02-12 11:24:20.848207",
  "modified_by": "Administrator", 
  "module": "HR", 
  "name": "Salary Slip",