Changed the build image to standard 5.0

* 6.0 includes Node 16 only, not 14. Using Standard 5.0 in order to be consistent with the stated requirements.

Author: josebagar

lib/pipeline-stack.ts

@@ -74,7 +74,7 @@ export class PipelineStack extends Stack {
         },
       }),
       environment: {
-        buildImage: LinuxBuildImage.STANDARD_6_0,
+        buildImage: LinuxBuildImage.STANDARD_5_0,
       },
       encryptionKey: key
     });
@@ -101,7 +101,7 @@ export class PipelineStack extends Stack {
         },
       }),
       environment: {
-        buildImage: LinuxBuildImage.STANDARD_6_0,
+        buildImage: LinuxBuildImage.STANDARD_5_0,
       },
       encryptionKey: key
     });