[CI] Small adjustments to the Windows actions

# Motivation

There were two small problems:
1. The CI for the nightlies wasn't properly skipped
2. The name for the matrix wasn't applied in the case where it was skipped

# Modification

This PR hopefully fixes both issues.

.github/workflows/swift_matrix.yml

@@ -151,7 +151,6 @@ jobs:
   windows:
     name: Windows (${{ matrix.swift.swift_version }})
     runs-on: windows-2022
-    if: ${{ inputs.matrix_windows_6_0_enabled }}
     strategy:
       fail-fast: false
       matrix:
@@ -160,6 +159,7 @@ jobs:
           - image: swift:6.0-windowsservercore-ltsc2022
             swift_version: "6.0"
             enabled: ${{ inputs.matrix_windows_6_0_enabled }}
+    if: ${{ inputs.matrix_windows_6_0_enabled }}
     steps:
       - name: Pull Docker image
         if: ${{ matrix.swift.enabled }}
@@ -180,7 +180,6 @@ jobs:
   windows-nightly:
     name: Windows (${{ matrix.swift.swift_version }})
     runs-on: windows-2019
-    if: ${{ inputs.matrix_windows_nightly_6_0_enabled }} && ${{ inputs.matrix_windows_nightly_main_enabled }}
     strategy:
       fail-fast: false
       matrix:
@@ -192,6 +191,7 @@ jobs:
           - image: swiftlang/swift:nightly-main-windowsservercore-1809
             swift_version: "nightly-main"
             enabled: ${{ inputs.matrix_windows_nightly_main_enabled }}
+    if: ${{ inputs.matrix_windows_nightly_6_0_enabled }} || ${{ inputs.matrix_windows_nightly_main_enabled }}
     steps:
       - name: Pull Docker image
         if: ${{ matrix.swift.enabled }}