Show regional age error for under-13 users in restricted regions

When a region has a stricter minimum age than the global minimum (e.g.,
16 in Australia), users entering a birthdate below 13 were shown the
global "must be 13" message instead of the regional "must be 16" one.

Select the message based on whether the region has a stricter minimum,
not on which threshold the user falls under. Any birthdate below the
regional minimum now consistently shows the regional message.

src/screens/Signup/StepInfo/index.tsx

@@ -308,16 +308,16 @@ export function StepInfo({
                     <Admonition.Icon />
                     <Admonition.Content>
                       <Admonition.Text>
-                        {!isOverAppMinAccessAge ? (
-                          <Plural
-                            value={MIN_ACCESS_AGE}
-                            other="You must be # years of age or older to create an account."
-                          />
-                        ) : (
+                        {aaRegionConfig.minAccessAge > MIN_ACCESS_AGE ? (
                           <Plural
                             value={aaRegionConfig.minAccessAge}
                             other="You must be # years of age or older to create an account in your region."
                           />
+                        ) : (
+                          <Plural
+                            value={MIN_ACCESS_AGE}
+                            other="You must be # years of age or older to create an account."
+                          />
                         )}
                       </Admonition.Text>
                       {IS_NATIVE &&