Minor correction to error message (#426)

Related to iterative/dvc#9821

---------

Co-authored-by: Dave Berenbaum <dave.berenbaum@gmail.com>

gto/constants.py

@@ -71,17 +71,17 @@ def check_string_is_valid(value, regex=name_re):
 def assert_name_is_valid(value):
     if not check_string_is_valid(value, regex=name_re):
         raise ValidationError(
-            f"Invalid value '{value}'. Only lowercase english letters, , '-', '/' are allowed."
-            "Value must be of len >= 2, must with a letter and end with a letter or a number."
+            f"Invalid value '{value}'. Only letters, numbers, '_', '-', '/' are allowed."
+            "Value must be of len >= 2 and must start and end with a letter or a number."
         )
 
 
 def assert_fullname_is_valid(value):
     if not check_string_is_valid(value, regex=fullname_re):
         # fix error message to be regex-specific
         raise ValidationError(
-            f"Invalid value '{value}'. Only lowercase english letters, , '-', '/' are allowed."
-            "Value must be of len >= 2, must start with a letter and end with a letter or a number."
+            f"Invalid value '{value}'. Only letters, numbers, '_', '-', '/' are allowed."
+            "Value must be of len >= 2 and must start and end with a letter or a number."
         )