[wasm] Move Scenario=BuildWasmApps to be submitted first

TLDR;
- this might help with the job getting scheduled first, and thus having
  a chance at completing at the same time as others.

Reasoning:

The problem this is trying to fix is:

1. The helix step submits 3 jobs:
    a. library tests to be run with v8
    b. library tests to be run with browser (scenario=wasmtestonbrowser)
    c. Wasm.Build.Tests (scenario=buildwasmapps)

2. The 3 jobs, individually take roughly 30mins each
3. And they get submitted at roughly the same time
4. But .. the first two seem to complete earlier, and the 3rd one
   completes 25-30mins later.

The hypothesis is that all the machines might be busy processing the
200+ work items from each of the first two steps, and so
Wasm.Build.Tests get scheduled pretty late.

So, here we move that to be submitted first, in the hope that it would
be able to run in parallel with the other jobs.

eng/pipelines/runtime.yml

@@ -293,9 +293,9 @@ jobs:
         creator: dotnet-bot
         testRunNamePrefixSuffix: Mono_$(_BuildConfig)
         scenarios:
+        - buildwasmapps
         - normal
         - wasmtestonbrowser
-        - buildwasmapps
         condition: >-
           or(
           eq(variables['librariesContainsChange'], true),