fix test

Author: jacquesguan

mlir/test/Conversion/ArithToEmitC/arith-to-emitc-unsupported.mlir

@@ -161,7 +161,7 @@ func.func @arith_truncf(%arg0: f64) -> f32 {
 // -----
 
 func.func @arith_extf_f128(%arg0: f32) -> f128 {
-  // expected-error @+1 {{failed to legalize operation 'arith.truncf'}}
+  // expected-error @+1 {{failed to legalize operation 'arith.extf'}}
   %extd = arith.extf %arg0 : f32 to f128
   return %extd : f128
 }
@@ -177,7 +177,7 @@ func.func @arith_truncf_f128(%arg0: f128) -> f32 {
 // -----
 
 func.func @arith_extf_vector(%arg0: vector<4xf32>) -> vector<4xf64> {
-  // expected-error @+1 {{failed to legalize operation 'arith.truncf'}}
+  // expected-error @+1 {{failed to legalize operation 'arith.extf'}}
   %extd = arith.extf %arg0 : vector<4xf32> to vector<4xf64>
   return %extd : vector<4xf64>
 }