Warning when building ret-sync Ghidra extension

Minor but should be fixed next time we update the Ghidra extension.

```
ret-sync/ext_ghidra/src/main/java/retsync/RetSyncPlugin.java`

- [warn] Java compilation warning`:444:54-12`
`ret-sync/ext_ghidra/src/main/java/retsync/RetSyncPlugin.java:444: warning: [removal] EOL_COMMENT in CodeUnit has been deprecated and marked for removal`
`            cmd = new AppendCommentCmd(dest, CodeUnit.EOL_COMMENT, msg, ";");`
`                                                     ^`
EOL_COMMENT in ghidra.program.model.listing.CodeUnit has been deprecated and marked for removal
- [warn] Java compilation warning`:444:19-58`
`ret-sync/ext_ghidra/src/main/java/retsync/RetSyncPlugin.java:444: warning: [removal] AppendCommentCmd(Address,int,String,String) in AppendCommentCmd has been deprecated and marked for removal`
`            cmd = new AppendCommentCmd(dest, CodeUnit.EOL_COMMENT, msg, ";");`
`                  ^`
AppendCommentCmd(ghidra.program.model.address.Address,int,java.lang.String,java.lang.String) in ghidra.app.cmd.comments.AppendCommentCmd has been deprecated and marked for removal
- [warn] Java compilation warning`:487:51-12`
`ret-sync/ext_ghidra/src/main/java/retsync/RetSyncPlugin.java:487: warning: [removal] EOL_COMMENT in CodeUnit has been deprecated and marked for removal`
`            cmd = new SetCommentCmd(dest, CodeUnit.EOL_COMMENT, "");`
`                                                  ^`
EOL_COMMENT in ghidra.program.model.listing.CodeUnit has been deprecated and marked for removal
- [warn] Java compilation warning`:487:19-49`
`ret-sync/ext_ghidra/src/main/java/retsync/RetSyncPlugin.java:487: warning: [removal] SetCommentCmd(Address,int,String) in SetCommentCmd has been deprecated and marked for removal`
`            cmd = new SetCommentCmd(dest, CodeUnit.EOL_COMMENT, "");`
`                  ^`
SetCommentCmd(ghidra.program.model.address.Address,int,java.lang.String) in ghidra.app.cmd.comments.SetCommentCmd has been deprecated and marked for removal
- [advice] Java compilation note
`Note: ret-sync/ext_ghidra/src/main/java/retsync/RetSyncPlugin.java uses unchecked or unsafe operations.`
ret-sync/ext_ghidra/src/main/java/retsync/RetSyncPlugin.java uses unchecked or unsafe operations.
- [advice] Java compilation note
`Note: Recompile with -Xlint:unchecked for details.`
Recompile with -Xlint:unchecked for details.

- `:compileJava`

- [warn] Java compilation warning`:compileJava`
`ret-sync/ext_ghidra/src/main/java/retsync/RetSyncPlugin.java:444: warning: [removal] EOL_COMMENT in CodeUnit has been deprecated and marked for removal`
`            cmd = new AppendCommentCmd(dest, CodeUnit.EOL_COMMENT, msg, ";");`
`                                                     ^`
EOL_COMMENT in ghidra.program.model.listing.CodeUnit has been deprecated and marked for removal
```