Remove httpPath from default test config fixture in otel_logs_source

[oeyh]

Description

Follow-up to #6572 so that GrpcTest doesn't use httpPath. The new httpPath and http service are tested in the HttpTest class.

Issues Resolved

N/A

Check List

• New functionality includes testing.
• New functionality has a documentation issue. Please link to it in this PR.
  • New functionality has javadoc added
• Commits are signed with a real name per the DCO

By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.
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[opensearch-trigger-bot]

The backport to 2.14 failed:

The process '/usr/bin/git' failed with exit code 1

To backport manually, run these commands in your terminal:

# Fetch latest updates from GitHub
git fetch
# Create a new working tree
git worktree add .worktrees/backport-2.14 2.14
# Navigate to the new working tree
cd .worktrees/backport-2.14
# Create a new branch
git switch --create backport/backport-6575-to-2.14
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 06603180ee4637e276a8430324f301ec32e8d793
# Push it to GitHub
git push --set-upstream origin backport/backport-6575-to-2.14
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.14

Then, create a pull request where the base branch is 2.14 and the compare/head branch is backport/backport-6575-to-2.14.

[oeyh]

This is the manual backport step I followed:

# Fetch latest updates from GitHub
git fetch upstream
# Create a new working tree
git worktree add .worktrees/backport-2.14 upstream/2.14
# Navigate to the new working tree
cd .worktrees/backport-2.14
# Create a new branch
git switch --create backport/backport-6575-to-2.14
# Cherry-pick the merged commit of this pull request and resolve the conflicts
git cherry-pick -x --mainline 1 06603180ee4637e276a8430324f301ec32e8d793
# Push it to GitHub
git push --set-upstream origin backport/backport-6575-to-2.14
# Go back to the original working tree
cd ../..
# Delete the working tree
git worktree remove .worktrees/backport-2.14