Fix invalid expression syntax

The expression had an extra '$' character which made it always evaluate to true.

See https://github.com/boostsecurityio/poutine/blob/main/docs/content/en/rules/if_always_true.md.

CLA: trivial

Reviewed-by: Neil Horman <nhorman@openssl.org>
Reviewed-by: Paul Dale <ppzgs1@gmail.com>
(Merged from #24325)

.github/workflows/windows.yml

@@ -66,7 +66,7 @@ jobs:
       run: nmake test VERBOSE_FAILURE=yes TESTS=-test_fuzz* HARNESS_JOBS=4
     - name: install
       # Run on 64 bit only as 32 bit is slow enough already
-      if: $${{ matrix.platform.arch == 'win64' }}
+      if: ${{ matrix.platform.arch == 'win64' }}
       run: |
         mkdir _dest
         nmake install DESTDIR=_dest