fix(profiling): avoid possible circular import [backport 1.20] (#7059)

Backport 518365c from #7038 to 1.20.

I'm not 100% sure why this is suddenly happening, but sometimes we get
an error in pprof.pyx because the `sanitize_string` name cannot be
imported.

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## Reviewer Checklist

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Co-authored-by: David Sanchez <[email protected]>

Author: github-actions[bot]

ddtrace/profiling/exporter/pprof.pyx

@@ -12,7 +12,7 @@ from ddtrace import ext
 from ddtrace.internal import packages
 from ddtrace.internal._encoding import ListStringTable as _StringTable
 from ddtrace.internal.compat import ensure_str
-from ddtrace.internal.datadog.profiling.ddup import sanitize_string
+from ddtrace.internal.datadog.profiling.utils import sanitize_string
 from ddtrace.internal.utils import config
 from ddtrace.profiling import event
 from ddtrace.profiling import exporter