bug(golang-rewrite): Excessive new lines when using the asdf set command

[AlfredoRamos]

Describe the Bug

When running asdf set multiple times for the same plugin, it keeps adding unnecessary new lines.

Steps to Reproduce

1. Run the following commands:

   asdf set nodejs 23.4.0
   asdf set nodejs 23.5.0
   asdf set nodejs 23.6.0

2. See the content of .tool-versions:

   cat -A .tool-versions

Note: Added the -A flag in the cat command just for clarification about the new lines.

Expected Behaviour

nodejs 23.6.0$

Actual Behaviour

nodejs 23.6.0$
$
$

Environment

OS:
Linux arch-linux 6.12.9-arch1-1 #1 SMP PREEMPT_DYNAMIC Fri, 10 Jan 2025 00:39:41 +0000 x86_64 GNU/Linux

SHELL:
GNU bash, version 5.2.37(1)-release (x86_64-pc-linux-gnu)
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>

This is free software; you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

BASH VERSION:
5.2.37(1)-release

ASDF VERSION:
v0.15.0-58a9e25

ASDF INTERNAL VARIABLES:
ASDF_DEFAULT_TOOL_VERSIONS_FILENAME=.tool-versions
ASDF_DATA_DIR=/home/alfredo/.asdf
ASDF_CONFIG_FILE=/home/alfredo/.asdfrc

ASDF INSTALLED PLUGINS:
nodejs    https://github.com/asdf-vm/asdf-nodejs.git 93bd217ba74f05080eebb7d8e1c146a385b01d7f

asdf plugins affected (if relevant)

No response