Remove unnecessary function override

Signed-off-by: Gabor Mezei <gabor.mezei@arm.com>
diff --git a/scripts/mbedtls_dev/ecp.py b/scripts/mbedtls_dev/ecp.py
index e01b80f..6440ba0 100644
--- a/scripts/mbedtls_dev/ecp.py
+++ b/scripts/mbedtls_dev/ecp.py
@@ -72,10 +72,6 @@
         result = self.int_a % self.int_n
         return [self.format_result(result)]
 
-    @property
-    def is_valid(self) -> bool:
-        return True
-
 class EcpP224R1Raw(bignum_common.ModOperationCommon,
                    EcpTarget):
     """Test cases for ecp quasi_reduction()."""
@@ -137,10 +133,6 @@
         result = self.int_a % self.int_n
         return [self.format_result(result)]
 
-    @property
-    def is_valid(self) -> bool:
-        return True
-
 class EcpP521R1Raw(bignum_common.ModOperationCommon,
                    EcpTarget):
     """Test cases for ecp quasi_reduction()."""
@@ -227,7 +219,3 @@
     def result(self) -> List[str]:
         result = self.int_a % self.int_n
         return [self.format_result(result)]
-
-    @property
-    def is_valid(self) -> bool:
-        return True