fix: relabel rate to tax rate

(cherry picked from commit 1eb8b0c)

Author: mahsem

erpnext/accounts/doctype/account/account.json

@@ -128,7 +128,7 @@
    "description": "Rate at which this tax is applied",
    "fieldname": "tax_rate",
    "fieldtype": "Float",
-   "label": "Rate",
+   "label": "Tax Rate",
    "oldfieldname": "tax_rate",
    "oldfieldtype": "Currency"
   },

erpnext/accounts/doctype/advance_taxes_and_charges/advance_taxes_and_charges.json

@@ -101,7 +101,7 @@
    "fieldname": "rate",
    "fieldtype": "Float",
    "in_list_view": 1,
-   "label": "Rate",
+   "label": "Tax Rate",
    "oldfieldname": "rate",
    "oldfieldtype": "Currency"
   },

erpnext/accounts/doctype/pos_closing_entry_taxes/pos_closing_entry_taxes.json

@@ -14,7 +14,7 @@
    "fieldname": "rate",
    "fieldtype": "Percent",
    "in_list_view": 1,
-   "label": "Rate",
+   "label": "Tax Rate",
    "read_only": 1
   },
   {