MDL-71011 adodb: Update readme and thirdpartylibs

Small changes in readme and document the bump in xml

lib/adodb/readme_moodle.txt

@@ -1,8 +1,9 @@
-Description of ADODB V5.20.16 library import into Moodle
+Description of ADOdb v5.21.0 library import into Moodle 3.11 and up
 
-This library will be probably removed in Moodle 2.1,
-it is now used only in enrol and auth db plugins.
-The core DML drivers are not using ADODB any more.
+Source: https://github.com/ADOdb/ADOdb
+
+This library will be probably removed sometime in the future
+because it is now used only by enrol and auth db plugins.
 
 Removed:
  * Any invisible file (dot suffixed)
@@ -11,21 +12,17 @@ Removed:
  * cute_icons_for_site/ (if present)
  * docs/
  * lang/* everything but adodb-en.inc.php (originally because they were not utf-8, now because of not used)
+ * nbproject/ (if present)
  * pear/
-
-
-
- * nbproject/
  * replicate/
  * scripts/
+ * server.php
  * session/
  * tests/
- * server.php
- * lang/* except en (because they were not in utf8)
 
 Added:
  * index.html - prevent directory browsing on misconfigured servers
  * readme_moodle.txt - this file ;-)
 
-Our changes:
- * MDL-67034 Fixes to make the library php74 compliant.
+Our changes (to be checked on next update if they are already applied upstream)::
+ * https://github.com/ADOdb/ADOdb/issues/711

lib/thirdpartylibs.xml

@@ -3,9 +3,9 @@
   <library>
     <location>adodb</location>
     <name>AdoDB</name>
-    <license>BSD/GPL</license>
-    <version>5.20.16</version>
-    <licenseversion>2.1+</licenseversion>
+    <license>BSD/LGPL</license>
+    <version>5.21.0</version>
+    <licenseversion>3-Clause/2.1+</licenseversion>
   </library>
   <library>
     <location>behat/axe</location>