chore: dont flag node_modules or package-lock as generated

Now that we make dependency upgrades as pull requests, this should make
them easier to review since GitHub will now render diffs for them by
default.

PR-URL: #3991
Credit: @lukekarrys
Close: #3991
Reviewed-by: @wraithgar

.gitattributes

@@ -0,0 +1,2 @@
+/node_modules/**    linguist-generated=false
+/package-lock.json  linguist-generated=false