revert(metrics): typing regression on log_metrics callable

[heitorlessa]

Issue #, if available: #743

Description of changes:

Fixes a typing regression for log_metrics where the return had an explicit Callable and this confuses MyPy and loses the param spec.

from aws_lambda_powertools import Metrics
from aws_lambda_powertools.utilities.typing import LambdaContext

metrics = Metrics(namespace="test")


@metrics.log_metrics
def lambda_handler(evt: dict, ctx: LambdaContext):
    metrics.add_metric(name="test", unit="Count", value=1)

Error

$ mypy ~/Library/Application\ Support/JetBrains/PyCharm2021.2/scratches/scratch.py
/Users/lessa/Library/Application Support/JetBrains/PyCharm2021.2/scratches/scratch.py:11:1: error: <nothing> not callable  [misc]
/Users/lessa/Library/Application Support/JetBrains/PyCharm2021.2/scratches/scratch.py:12:1: error: <nothing> not callable  [misc]
Found 2 errors in 1 file (checked 1 source file)

Checklist

• Meet tenets criteria
• Update tests
• Update docs
• PR title follows conventional commit semantics

Breaking change checklist

RFC issue #:

• Migration process documented
• Implement warnings (if it can live side by side)

By submitting this pull request, I confirm that you can use, modify, copy, and redistribute this contribution, under the terms of your choice.

[codecov-commenter]

Codecov Report

Merging #744 (9b0ba28) into develop (97c9423) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@             Coverage Diff             @@
##           develop     #744      +/-   ##
===========================================
- Coverage    99.77%   99.77%   -0.01%     
===========================================
  Files          117      117              
  Lines         4922     4921       -1     
  Branches       271      271              
===========================================
- Hits          4911     4910       -1     
  Misses           9        9              
  Partials         2        2              

Impacted Files	Coverage Δ
aws_lambda_powertools/metrics/metrics.py	100.00% <100.00%> (ø)

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