fix(profiling): tag serialisation in HTTP exporter [backport 2.8] (#9042

)

Backport 0bacde0 from #9032 to 2.8.

Ensure that the HTTP exporter does not fail to serialise the tags.

Addresses #8996.

## Checklist

- [x] Change(s) are motivated and described in the PR description
- [x] Testing strategy is described if automated tests are not included
in the PR
- [x] Risks are described (performance impact, potential for breakage,
maintainability)
- [x] Change is maintainable (easy to change, telemetry, documentation)
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guidelines](https://ddtrace.readthedocs.io/en/stable/releasenotes.html)
are followed or label `changelog/no-changelog` is set
- [x] Documentation is included (in-code, generated user docs, [public
corp docs](https://github.com/DataDog/documentation/))
- [x] Backport labels are set (if
[applicable](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting))
- [x] If this PR changes the public interface, I've notified
`@DataDog/apm-tees`.

## Reviewer Checklist

- [x] Title is accurate
- [x] All changes are related to the pull request's stated goal
- [x] Description motivates each change
- [x] Avoids breaking
[API](https://ddtrace.readthedocs.io/en/stable/versioning.html#interfaces)
changes
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- [x] Change is maintainable (easy to change, telemetry, documentation)
- [x] Release note makes sense to a user of the library
- [x] Author has acknowledged and discussed the performance implications
of this PR as reported in the benchmarks PR comment
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[release branch maintenance
policy](https://ddtrace.readthedocs.io/en/latest/contributing.html#backporting)

Co-authored-by: Gabriele N. Tornetta <P403n1x87@users.noreply.github.com>

ddtrace/profiling/exporter/http.py

@@ -152,7 +152,7 @@ def _get_tags(
 
         tags.update(self.tags)
 
-        return ",".join(tag + ":" + value for tag, value in tags.items())
+        return ",".join(f"{tag}:{value}" for tag, value in tags.items())
 
     def export(
         self,

releasenotes/notes/fix-profiling-exporter-tags-f19c6cf93cbe1502.yaml

@@ -0,0 +1,4 @@
+---
+fixes:
+  - |
+    profiling: fix a bug that caused the HTTP exporter to crash when attempting to serialize tags.