BUG: variable interpolation runs twice for taskfiles that are included as a mapping

[sprig]

[Edit: typo]
Hi. Thanks for this great tool!

Consider the following pair of taskfiles:

## Taskfile.yml
version: '3'

includes:
  test: test
#  test:
#    taskfile: test

and

## test/Taskfile.yml
version: '3'

vars:
  BAR: FOO/{{.BAR}}

tasks:
  foobar: echo {{.BAR}}

and run task test:foobar:

$ BAR=BAZ task test:foobar
task: [test:foobar] echo FOO/BAZ
FOO/BAZ

Looks good so far. Now uncomment the commented lines in the root taskfile above. remove the original include definition, and rerun the above test:

$ BAR=BAZ task test:foobar
task: [test:foobar] echo FOO/FOO/BAZ
FOO/FOO/BAZ

oops.

• Task version:

$ task --version
Task version: v3.36.0 (h1:XVJ5hQ5hdzTAulHpAGzbUMUuYr9MUOEQFOFazI3hUsY=)

• Operating system:
  linux
• Experiments enabled:

$ task --experiments
* GENTLE_FORCE:         off
* REMOTE_TASKFILES: off
* ANY_VARIABLES:    off