Fix typo in flex and composite error message.

PiperOrigin-RevId: 611115238
Change-Id: Iadb9b4b078e60bca15184f3435380eb67b2da8a9

src/user/user_composite.cc

@@ -342,7 +342,7 @@ bool mjCComposite::Make(mjCModel* model, mjmBody* body, char* error, int error_s
     return MakeBox(model, body, error, error_sz);
 
   default:
-    return comperr(error, "Uknown shape in composite", error_sz);
+    return comperr(error, "Unknown shape in composite", error_sz);
   }
 }
 

src/user/user_flexcomp.cc

@@ -155,7 +155,7 @@ bool mjCFlexcomp::Make(mjCModel* model, mjmBody* body, char* error, int error_sz
     break;
 
   default:
-    return comperr(error, "Uknown flexcomp type", error_sz);
+    return comperr(error, "Unknown flexcomp type", error_sz);
   }
   if (!res) {
     return false;

test/user/user_flex_test.cc

@@ -161,7 +161,7 @@ TEST_F(UserFlexTest, PointAndElementNotInDirect) {
   EXPECT_THAT(error.data(), HasSubstr("Point and element required"));
 }
 
-TEST_F(UserFlexTest, UknownFlexCompType) {
+TEST_F(UserFlexTest, UnknownFlexCompType) {
   static constexpr char xml[] = R"(
   <mujoco>
   <worldbody>