[hotfix] Fix environment variable check for FLINK_CDC_HOME in YarnApplicationDeploymentExecutor. (#4012)

Author: joyCurry30

flink-cdc-composer/src/main/java/org/apache/flink/cdc/composer/flink/deployment/YarnApplicationDeploymentExecutor.java

@@ -127,7 +127,7 @@ private String getFlinkCDCDistJarFromEnv() throws IOException {
         Preconditions.checkNotNull(
                 flinkCDCHomeFromEnvVar,
                 "FLINK_CDC_HOME is not correctly set in environment variable, current FLINK_CDC_HOME is: "
-                        + FLINK_CDC_HOME_ENV_VAR);
+                        + flinkCDCHomeFromEnvVar);
         Path flinkCDCLibPath = new Path(flinkCDCHomeFromEnvVar, "lib");
         if (!flinkCDCLibPath.getFileSystem().exists(flinkCDCLibPath)
                 || !flinkCDCLibPath.getFileSystem().getFileStatus(flinkCDCLibPath).isDir()) {