fixes validation

Author: juanfriss

lob_python/model/letter.py

@@ -97,12 +97,12 @@ class Letter(ModelNormal):
     }
 
     validations = {
-        ('file_template_id',): {
+        ('template_id',): {
             'regex': {
                 'pattern': r'^tmpl_[a-zA-Z0-9]+$',  # noqa: E501
             },
         },
-        ('file_template_version_id',): {
+        ('template_version_id',): {
             'regex': {
                 'pattern': r'^vrsn_[a-zA-Z0-9]+$',  # noqa: E501
             },