feat: Remove nodejs6.10 init template (#1505)

Since April 30, 2019, it's no longer possible to create new functions using nodejs6.10 https://docs.aws.amazon.com/lambda/latest/dg/runtime-support-policy.html.

samcli/local/common/runtime_template.py

@@ -34,13 +34,7 @@
             "dependency_manager": "npm",
             "init_location": os.path.join(_templates, "cookiecutter-aws-sam-hello-nodejs"),
             "build": True,
-        },
-        {
-            "runtimes": ["nodejs6.10"],
-            "dependency_manager": "npm",
-            "init_location": os.path.join(_templates, "cookiecutter-aws-sam-hello-nodejs6"),
-            "build": True,
-        },
+        }
     ],
     "dotnet": [
         {
@@ -83,7 +77,6 @@
     "nodejs12.x": ["npm"],
     "nodejs10.x": ["npm"],
     "nodejs8.10": ["npm"],
-    "nodejs6.10": ["npm"],
     "dotnetcore2.1": ["cli-package"],
     "dotnetcore2.0": ["cli-package"],
     "dotnetcore1.0": ["cli-package"],
@@ -115,7 +108,6 @@
     # older nodejs runtimes
     "nodejs10.x",
     "nodejs8.10",
-    "nodejs6.10",
     # older python runtimes
     "python3.7",
     "python3.6",