`files.block` duplicates end marker when overwriting existing block

[stone-w4tch3r]

Describe the bug

If file with marked block already exists, but content is not what expected, files.block will append redundant marker line after block

To Reproduce

1. On remote:

   touch file && echo "hello
   #### BEGIN BLOCK ####
   ---
   #### END BLOCK ####
   bye" > file

2. Run main.py:

   
   from pyinfra.operations import files

files.block( path="/home/ubuntu/file", content="blah blah", marker="#### {mark} BLOCK ####", )

3. See result on remote:
NOTE:  due to #1028 `file.block` adds a `$`, but even after fixing this behavior issue with redundant marker persists
```bash
cat file
hello
#### BEGIN BLOCK ####
$blah blah
#### END BLOCK ####
#### END BLOCK ####
bye

• Target system information Ubuntu 20.04.6 LTS (GNU/Linux 5.4.0-164-generic x86_64)

Expected behavior

No duplication after running operation

Meta

• Include output of pyinfra --support.

  pyinfra --support  
  --> Support information:
  
  If you are having issues with pyinfra or wish to make feature requests, please
  check out the GitHub issues at https://github.com/Fizzadar/pyinfra/issues .
  When adding an issue, be sure to include the following:
  
  System: Linux
    Platform: Linux-6.2.0-36-generic-x86_64-with-glibc2.37
    Release: 6.2.0-36-generic
    Machine: x86_64
  pyinfra: v2.8
  Executable: /home/user/Projects/linux_stuff/pyinfra_manager/venv/bin/pyinfra
  Python: 3.11.4 (CPython, GCC 12.3.0)

• How was pyinfra installed (source/pip)? pip
• Include pyinfra-debug.log (if one was created) None
• Consider including output with -vv and --debug.

  --> Starting operation: Files/Block (path=/home/ubuntu/file, content=blah blah, marker=#### {mark} BLOCK ####)
  [primary.multipass] >>> env SUDO_ASKPASS=/tmp/pyinfra-sudo-askpass-Oa63swn8q5QA *** sh -c 'OUT="$(TMPDIR=/tmp mktemp -t pyinfra.XXXXXX)" &&  awk '"'"'BEGIN {{f=1; x=ARGV[2]; ARGV[2]=""}}/#### BEGIN BLOCK ####/ {print; print x; f=0} /#### END BLOCK ####/ {print; f=1} f'"'"' /home/ubuntu/file $"blah blah" > $OUT && chmod $(stat -c %a /home/ubuntu/file 2>/dev/null || stat -f %Lp /home/ubuntu/file ) $OUT &&  (chown $(stat -c "%U:%G" /home/ubuntu/file 2>/dev/null) $OUT ||  chown -n $(stat -f "%u:%g" /home/ubuntu/file ) $OUT)  && mv "$OUT" /home/ubuntu/file'
  [primary.multipass] Success

[stone-w4tch3r]

Issue is in final awk code: awk 'BEGIN {{f=1; x=ARGV[2]; ARGV[2]=""}}/#### BEGIN BLOCK ####/ {print; print x; f=0} /#### END BLOCK ####/ {print; f=1} f' ...