chore(iast): disable error log metric (#10803)

Disable the "Tainted Map isn't initialized" error log metric. This
message is triggered when taint occurs outside the request, making it
redundant.

No release note is required, as this error occurs after PR #10740, which
has not been released yet.

Task APPSEC-55018

## Checklist
- [x] PR author has checked that all the criteria below are met
- The PR description includes an overview of the change
- The PR description articulates the motivation for the change
- The change includes tests OR the PR description describes a testing
strategy
- The PR description notes risks associated with the change, if any
- Newly-added code is easy to change
- The change follows the [library release note
guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
- The change includes or references documentation updates if necessary
- Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))

## Reviewer Checklist
- [x] Reviewer has checked that all the criteria below are met
- Title is accurate
- All changes are related to the pull request's stated goal
- Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
- Testing strategy adequately addresses listed risks
- Newly-added code is easy to change
- Release note makes sense to a user of the library
- If necessary, author has acknowledged and discussed the performance
implications of this PR as reported in the benchmarks PR comment
- Backport labels are set in a manner that is consistent with the
[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

(cherry picked from commit 99428de)

ddtrace/appsec/_iast/_taint_tracking/__init__.py

@@ -159,7 +159,7 @@ def taint_pyobject(pyobject: Any, source_name: Any, source_value: Any, source_or
         _set_metric_iast_executed_source(source_origin)
         return pyobject_newid
     except ValueError as e:
-        iast_taint_log_error("Tainting object error (pyobject type %s): %s" % (type(pyobject), e))
+        log.debug("Tainting object error (pyobject type %s): %s", type(pyobject), e)
     return pyobject
 
 

tests/appsec/iast/aspects/test_add_aspect.py

@@ -236,11 +236,11 @@ def test_add_aspect_tainting_add_left_twice(obj1, obj2):
 @pytest.mark.parametrize(
     "log_level, iast_debug, expected_log_msg",
     [
-        (logging.DEBUG, "", ""),
+        (logging.DEBUG, "", "Tainting object error"),
         (logging.WARNING, "", ""),
-        (logging.DEBUG, "false", ""),
+        (logging.DEBUG, "false", "Tainting object error"),
         (logging.WARNING, "false", ""),
-        (logging.DEBUG, "true", "_iast/_taint_tracking/__init__.py"),
+        (logging.DEBUG, "true", "Tainting object error"),
         (logging.WARNING, "true", ""),
     ],
 )
@@ -271,7 +271,7 @@ def test_taint_object_error_with_no_context(log_level, iast_debug, expected_log_
     assert len(ranges_result) == 0
 
     if expected_log_msg:
-        assert any(expected_log_msg in record.message for record in caplog.records), [
+        assert any(record.message.startswith(expected_log_msg) for record in caplog.records), [
             record.message for record in caplog.records
         ]
     else: