Fix endsWith() to the correct version endswith() in mx_sdk_vm_impl.py

Apparently, the PR [[GR-70588] Include the GraalVM version rather than the Java version in the vendor version and basedir name](#12319) (i.e. [commit 270badf](270badf) introduced a Python type because it used `endsWith()` instead of  `endswith()`. This lets my builds fail.

It's strange that thiy typo hasn't been caught by any tests

Author: simonis

sdk/mx.sdk/mx_sdk_vm_impl.py

@@ -2994,7 +2994,7 @@ def base_jdk_version_info():
         if version_type == 'vendor':
             graalvm_suffix = ''
             if java_pre:
-                graalvm_suffix += '.' if graalvm_version.endsWith('dev') else '-'
+                graalvm_suffix += '.' if graalvm_version.endswith('dev') else '-'
                 graalvm_suffix += java_pre
         else:
             assert version_type == 'base-dir', version_type