test(NODE-5603): use npm 9 on eol node versions (#618)

Author: durran

.evergreen/config.yml

@@ -101,6 +101,7 @@ tasks:
       - func: fetch source
         vars:
           NODE_LTS_VERSION: 14
+          NPM_VERSION: 9
       - func: install dependencies
       - func: run tests
         vars:
@@ -112,6 +113,8 @@ tasks:
         vars:
           NODE_LTS_VERSION: 16
       - func: install dependencies
+        vars:
+          NPM_VERSION: 9
       - func: run tests
         vars:
           TEST_TARGET: node

.evergreen/install-dependencies.sh

@@ -2,6 +2,7 @@
 set -o errexit  # Exit the script with error if any of the commands fail
 
 NODE_LTS_VERSION=${NODE_LTS_VERSION:-14}
+NPM_VERSION=${NPM_VERSION:-latest}
 
 source "${PROJECT_DIRECTORY}/.evergreen/init-node-and-npm-env.sh"
 
@@ -94,8 +95,7 @@ else
 fi
 
 if [[ $operating_system != "win" ]]; then
-  # Update npm to latest when we can
-  npm install --global npm@latest
+  npm install --global npm@$NPM_VERSION
   hash -r
 fi