JVM IR: remove obsolete -Xir-check-local-names

This flag was added a long time ago, at the time when we weren't sure if
we were going to keep the naming of local and anonymous classes
completely equal to the naming in the old backend. Now that we've
decided that we won't keep it equal and there are a lot of differences
already, it's not useful anymore.

compiler/testData/cli/jvm/extraHelp.out

@@ -31,7 +31,6 @@ where advanced options include:
                              Works as `--enable-preview` in Java. All class files are marked as preview-generated thus it won't be possible to use them in release environment
   -Xfriend-paths=<path>      Paths to output directories for friend modules (whose internals should be visible)
   -Xmultifile-parts-inherit  Compile multifile classes as a hierarchy of parts and facade
-  -Xir-check-local-names     Check that names of local classes and anonymous objects are the same in the IR backend as in the old backend
   -Xmodule-path=<path>       Paths where to find Java 9+ modules
   -Xjava-package-prefix      Package prefix for Java files
   -Xjava-source-roots=<path> Paths to directories with Java source files