Remove HijriIran from HijriCalendarAlgorithm

To address https://github.com/unicode-org/icu4x/pull/6474/files/ea997a5a8a533d91fbfcddfdc4696c1be53cb3d4#r2059344445

Author: ebraminio

components/calendar/src/cal/hijri.rs

@@ -1299,10 +1299,8 @@ impl Calendar for HijriIran {
     }
 
     fn calendar_algorithm(&self) -> Option<crate::preferences::CalendarAlgorithm> {
-        let expected_calendar = crate::preferences::CalendarAlgorithm::Hijri(Some(
-            crate::preferences::HijriCalendarAlgorithm::HijriIran,
-        ));
-        Some(expected_calendar)
+        // There isn't any HijriCalendarAlgorithm entry associated with this right now, so
+        None
     }
 }
 
@@ -1526,7 +1524,6 @@ impl Date<HijriIran> {
     /// Construct new Hijri Iran Date.
     ///
     /// ```rust
-    /// use icu::calendar::cal::HijriIran;
     /// use icu::calendar::Date;
     ///
     /// let date_hijri =

components/locale_core/src/preferences/extensions/unicode/keywords/calendar.rs

@@ -20,9 +20,7 @@ enum_keyword!(
         /// Hijri calendar, tabular (intercalary years \[2,5,7,10,13,16,18,21,24,26,29] - civil epoch)
         Civil,
         /// Hijri calendar, Saudi Arabia sighting
-        Rgsa,
-        /// Hijri calendar, Iran sighting
-        HijriIran
+        Rgsa
 });
 
 #[cfg(feature = "alloc")]
@@ -58,8 +56,7 @@ enum_keyword!(
              ("umalqura" => Umalqura),
              ("tbla" => Tbla),
              ("civil" => Civil),
-             ("rgsa" => Rgsa),
-             ("iran" => HijriIran)
+             ("rgsa" => Rgsa)
         }),
         /// ISO calendar (Gregorian calendar using the ISO 8601 calendar week rules)
         ("iso8601" => Iso8601),