test: update test text to match what's being tested

spec/models/location_spec.rb

@@ -39,7 +39,7 @@ RSpec.describe Location, type: :model do
   describe "#units" do
     let(:location) { FactoryBot.build(:location) }
 
-    it "does add an error when the postcode is invalid" do
+    it "does add an error when the number of units is invalid" do
       location.units = nil
       expect { location.save! }
         .to raise_error(ActiveRecord::RecordInvalid, "Validation failed: Units #{I18n.t('activerecord.errors.models.location.attributes.units.blank')}")
@@ -49,7 +49,7 @@ RSpec.describe Location, type: :model do
   describe "#type_of_unit" do
     let(:location) { FactoryBot.build(:location) }
 
-    it "does add an error when the postcode is invalid" do
+    it "does add an error when the type of unit is invalid" do
       location.type_of_unit = nil
       expect { location.save! }
         .to raise_error(ActiveRecord::RecordInvalid, "Validation failed: Type of unit #{I18n.t('activerecord.errors.models.location.attributes.type_of_unit.blank')}")