Simplify UI copy

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

@@ -308,17 +308,10 @@ 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."
-                          />
-                        ) : (
-                          <Plural
-                            value={aaRegionConfig.minAccessAge}
-                            other="You must be # years of age or older to create an account in your region."
-                          />
-                        )}
+                        <Plural
+                          value={aaRegionConfig.minAccessAge}
+                          other="You must be # years of age or older to create an account in your region."
+                        />
                       </Admonition.Text>
                       {IS_NATIVE &&
                         !isDeviceGeolocationGranted &&