Version 6 / Drop support for Node 14 (which is EOL 4/30/23) (#196)

Node v14 is EOL, so we should drop support for it and upgrade
packages and testing accordingly.

Note this package has a dependency on `@apollo/utils.keyvaluecache`
which requires specifically node@>=16.14 due to its dependency on
`lru-cache`.

Author: trevor-scheer

.changeset/selfish-seals-worry.md

@@ -0,0 +1,9 @@
+---
+'@apollo/datasource-rest': major
+---
+
+Drop Node v14 support
+
+To take this major version, the only change necessary is to ensure your node runtime is using version 16.14.0 or later.
+
+Node v14 is EOL, so we should drop support for it and upgrade packages and testing accordingly. Note this package has a dependency on `@apollo/utils.keyvaluecache` which requires specifically node@>=16.14 due to its dependency on `lru-cache`.

.circleci/config.yml

@@ -74,9 +74,9 @@ workflows:
           matrix:
             parameters:
               node-version:
-                - "14"
                 - "16"
                 - "18"
+                - "20"
       - Prettier
       - Lint
       - Spell Check