Update jdt.core to I20200916-1800 (after merge of BETA_JAVA15)

- includes first set of fixes to reconcile Java 15 with OT/J
diff --git a/org.eclipse.jdt.core.tests.compiler/META-INF/MANIFEST.MF b/org.eclipse.jdt.core.tests.compiler/META-INF/MANIFEST.MF
index 6857c2a..0a4d623 100644
--- a/org.eclipse.jdt.core.tests.compiler/META-INF/MANIFEST.MF
+++ b/org.eclipse.jdt.core.tests.compiler/META-INF/MANIFEST.MF
@@ -2,7 +2,7 @@
 Bundle-ManifestVersion: 2
 Bundle-Name: %pluginName
 Bundle-SymbolicName: org.eclipse.jdt.core.tests.compiler;singleton:=true
-Bundle-Version: 3.12.1300.qualifier
+Bundle-Version: 3.12.1400.qualifier
 Bundle-Vendor: %providerName
 Bundle-Localization: plugin
 Export-Package: org.eclipse.jdt.core.tests.compiler,