DRIVERS-2612: Require 7.0+ for explain apiVersion bug fix (#1435)

In previous server versions, apiVersion is not properly appended to the root of an explain command document.

When testing with requireApiVersion=1, that can cause test failures if the driver does not have additional logic to always append the field to a crypt_shared/mongocryptd response.

Author: jmikola

source/client-side-encryption/etc/test-templates/explain.yml.template

@@ -1,5 +1,5 @@
 runOn:
-  - minServerVersion: "4.1.10"
+  - minServerVersion: "7.0.0"
 database_name: &database_name "default"
 collection_name: &collection_name "default"
 

source/client-side-encryption/tests/legacy/explain.json

@@ -1,7 +1,7 @@
 {
   "runOn": [
     {
-      "minServerVersion": "4.1.10"
+      "minServerVersion": "7.0.0"
     }
   ],
   "database_name": "default",

source/client-side-encryption/tests/legacy/explain.yml

@@ -1,5 +1,5 @@
 runOn:
-  - minServerVersion: "4.1.10"
+  - minServerVersion: "7.0.0"
 database_name: &database_name "default"
 collection_name: &collection_name "default"