feat(config): delete deprecated TrustStrategy.certFile() (#1650)

BREAKING CHANGE: the deprecated `org.neo4j.driver.Config.TrustStrategy#certFile()` has been deleted, please use `org.neo4j.driver.Config.TrustStrategy#certFiles()`.

Author: injectives

driver/clirr-ignored-differences.xml

@@ -800,4 +800,10 @@
         <method>org.neo4j.driver.reactive.ReactiveSession reactiveSession(org.neo4j.driver.SessionConfig)</method>
     </difference>
 
+    <difference>
+        <className>org/neo4j/driver/Config$TrustStrategy</className>
+        <differenceType>7002</differenceType>
+        <method>java.io.File certFile()</method>
+    </difference>
+
 </differences>

driver/src/main/java/org/neo4j/driver/Config.java

@@ -957,17 +957,6 @@ public Strategy strategy() {
             return strategy;
         }
 
-        /**
-         * Return the configured certificate file.
-         *
-         * @return configured certificate or {@code null} if trust strategy does not require a certificate.
-         * @deprecated superseded by {@link TrustStrategy#certFiles()}
-         */
-        @Deprecated
-        public File certFile() {
-            return certFiles.isEmpty() ? null : certFiles.get(0);
-        }
-
         /**
          * Return the configured certificate files.
          *