Update Fedora references in YML files from 42/40 to 43/42 (#121767)

Updates Fedora version references in CI/CD pipeline configuration files
for Helix testing infrastructure.

## Changes Made

- **Fedora Latest**: Updated from version 42 to 43
- **Fedora Oldest**: Updated from version 40 to 42

These changes update the Docker image references and platform
definitions used by the Helix testing infrastructure to test against
newer Fedora versions.

## Files Modified

- `eng/pipelines/helix-platforms.yml` - Updated both latest and oldest
Fedora version definitions
- `eng/pipelines/libraries/helix-queues-setup.yml` - Updated Fedora
reference used in extra-platforms CoreCLR testing

## Validation

- ✅ YAML syntax validated successfully
- ✅ No security vulnerabilities detected (CodeQL scan)
- ✅ Changes follow established patterns in the configuration files

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<details>

<summary>Original prompt</summary>

> Update Fedora references in *.yml files. I believe there are only two
relevant ones. They can be found by searching for "fedora-".
> 
> Where there is min and max, use 42 and 43, respectively. Where there
is a single choice, use 43.


</details>



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Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: richlander <2608468+richlander@users.noreply.github.com>

Author: Copilot

eng/pipelines/helix-platforms.yml

@@ -139,13 +139,13 @@ variables:
     value: (Debian.12.Amd64.Open)AzureLinux.3.Amd64.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:debian-12-helix-amd64
 
   # Fedora x64
-  # Latest: 42
+  # Latest: 43
   - name: helix_linux_x64_fedora_latest
-    value: (Fedora.42.Amd64.Open)AzureLinux.3.Amd64.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:fedora-42-helix-amd64
+    value: (Fedora.43.Amd64.Open)AzureLinux.3.Amd64.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:fedora-43-helix-amd64
 
-  # Oldest: 40
+  # Oldest: 42
   - name: helix_linux_x64_fedora_oldest
-    value: (Fedora.40.Amd64.Open)AzureLinux.3.Amd64.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:fedora-40-helix-amd64
+    value: (Fedora.42.Amd64.Open)AzureLinux.3.Amd64.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:fedora-42-helix-amd64
 
   # openSUSE x64
   # Latest: 15.6

eng/pipelines/libraries/helix-queues-setup.yml

@@ -62,7 +62,7 @@ jobs:
           - ${{ if and(eq(parameters.jobParameters.isExtraPlatformsBuild, true), ne(parameters.jobParameters.testScope, 'outerloop'))}}:
             # extra-platforms CoreCLR (inner loop only)
             - (Debian.13.Amd64.Open)AzureLinux.3.Amd64.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:debian-13-helix-amd64
-            - (Fedora.42.Amd64.Open)AzureLinux.3.Amd64.open@mcr.microsoft.com/dotnet-buildtools/prereqs:fedora-42-helix-amd64
+            - (Fedora.43.Amd64.Open)AzureLinux.3.Amd64.open@mcr.microsoft.com/dotnet-buildtools/prereqs:fedora-43-helix-amd64
             - (openSUSE.15.6.Amd64.Open)AzureLinux.3.Amd64.open@mcr.microsoft.com/dotnet-buildtools/prereqs:opensuse-15.6-helix-amd64
             - (Ubuntu.2604.Amd64.Open)AzureLinux.3.Amd64.Open@mcr.microsoft.com/dotnet-buildtools/prereqs:ubuntu-26.04-helix-amd64