fmt: Unnecessary expansion of if condition into a block

[charlieegan3]

opa fmt unnecessarily expands a one-liner if condition into a block (if { ... }) when the rule head's value expression spans multiple lines, even though the condition itself is a single simple term.

Steps To Reproduce

format this:

  foo := sprintf(
      "%d",
      1,
  ) if allow

and get this

  foo := sprintf(
      "%d",
      1,
  ) if {
      allow
  }

Expected behavior

remain as

  foo := sprintf(
      "%d",
      1,
  ) if allow