Correct log message format in AbstractDriverManagerConnectionSource (#3831)

* Correct log message format in AbstractDriverManagerConnectionSource

The debug log message in AbstractDriverManagerConnectionSource had 4 placeholders but was supplied with 5 arguments.
This corrects the format string to match the argument count, resolving the warning.

Fixes #3828

* Add changelog entry

Author: jhl221123

log4j-core/src/main/java/org/apache/logging/log4j/core/appender/db/jdbc/AbstractDriverManagerConnectionSource.java

@@ -160,7 +160,7 @@ public Connection getConnection() throws SQLException {
             connection = DriverManager.getConnection(actualConnectionString, toString(userName), toString(password));
         }
         LOGGER.debug(
-                "{} acquired connection for '{}': {} ({}{@})",
+                "{} acquired connection for '{}': {} ({}@{})",
                 getClass().getSimpleName(),
                 actualConnectionString,
                 connection,

src/changelog/.2.x.x/3828_fix_log_placeholder_mismatch.xml

@@ -0,0 +1,12 @@
+<?xml version="1.0" encoding="UTF-8"?>
+<entry xmlns="https://logging.apache.org/xml/ns"
+       xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance"
+       xsi:schemaLocation="
+           https://logging.apache.org/xml/ns
+           https://logging.apache.org/xml/ns/log4j-changelog-0.xsd"
+       type="fixed">
+    <issue id="3828" link="https://github.com/apache/logging-log4j2/issues/3828"/>
+    <description format="asciidoc">
+        Corrected an incorrect placeholder count in the AbstractDriverManagerConnectionSource debug log message to prevent unnecessary warnings.
+    </description>
+</entry>