connectionstring lowercase for kubernetes (#338)

src/Microsoft.Tye.Core/KubernetesManifestGenerator.cs

@@ -229,7 +229,7 @@ namespace Microsoft.Tye
                                             { "secretKeyRef", new YamlMappingNode()
                                                 {
                                                     { "name", new YamlScalarNode(binding.Name) { Style = ScalarStyle.SingleQuoted } },
-                                                    { "key", new YamlScalarNode("connectionString") { Style = ScalarStyle.SingleQuoted } },
+                                                    { "key", new YamlScalarNode("connectionstring") { Style = ScalarStyle.SingleQuoted } },
                                                 }
                                             },
                                         }

test/E2ETest/testassets/generate/generate-connectionstring-dependency.yaml

@@ -29,7 +29,7 @@ spec:
           valueFrom:
             secretKeyRef:
               name: 'binding-production-dependency-secret'
-              key: 'connectionString'
+              key: 'connectionstring'
         ports:
         - containerPort: 80
 ...