[IMP] partner_statement: remove "blocked" feature

If someone comes from v17 or older Odoo versions, and they still have "blocked" lines, there are three options for them:

- Develop glue module with another module that contains "blocked" field.
- Don't use this commit.
- Solve the "blocked" lines.

Good luck!

partner_statement/static/src/scss/layout_statement.scss

@@ -14,13 +14,6 @@
     }
 }
 
-.statement-blocked {
-    background-color: $gray-500 !important;
-    td:last-child {
-        background-color: $gray-500 !important;
-    }
-}
-
 .statement-reconciled {
     font-size: smaller;
     font-style: italic !important;