chore: operating-system -> os (#184)

Schema validation was flagging the old property name

.github/workflows/build-test.yml

@@ -13,10 +13,10 @@ on:
       
 jobs:
   build:
-    runs-on: ${{ matrix.operating-system }}
+    runs-on: ${{ matrix.os }}
     strategy:
       matrix:
-        operating-system: [ubuntu-latest, windows-latest, macos-latest]
+        os: [ubuntu-latest, windows-latest, macos-latest]
     steps:
       - uses: actions/checkout@v2
       - name: Setup node 12

.github/workflows/versions.yml

@@ -13,11 +13,11 @@ on:
       
 jobs:
   local-cache:
-    runs-on: ${{ matrix.operating-system }}
+    runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
-        operating-system: [ubuntu-latest, windows-latest, macos-latest]
+        os: [ubuntu-latest, windows-latest, macos-latest]
         node-version: [10, 12, 14]
     steps:
       - uses: actions/checkout@v2
@@ -30,11 +30,11 @@ jobs:
         shell: bash
 
   manifest:
-    runs-on: ${{ matrix.operating-system }}
+    runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
-        operating-system: [ubuntu-latest, windows-latest, macos-latest]
+        os: [ubuntu-latest, windows-latest, macos-latest]
         node-version: [10.15, 12.16.0, 14.2.0]
     steps:
       - uses: actions/checkout@v2
@@ -47,11 +47,11 @@ jobs:
         shell: bash
 
   check-latest:
-    runs-on: ${{ matrix.operating-system }}
+    runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
-        operating-system: [ubuntu-latest, windows-latest, macos-latest]
+        os: [ubuntu-latest, windows-latest, macos-latest]
         node-version: [10, 11, 12, 14]
     steps:
       - uses: actions/checkout@v2
@@ -65,11 +65,11 @@ jobs:
         shell: bash
 
   node-dist:
-    runs-on: ${{ matrix.operating-system }}
+    runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
-        operating-system: [ubuntu-latest, windows-latest, macos-latest]
+        os: [ubuntu-latest, windows-latest, macos-latest]
         node-version: [11, 13]
     steps:
       - uses: actions/checkout@v2
@@ -82,11 +82,11 @@ jobs:
         shell: bash
 
   old-versions:
-    runs-on: ${{ matrix.operating-system }}
+    runs-on: ${{ matrix.os }}
     strategy:
       fail-fast: false
       matrix:
-        operating-system: [ubuntu-latest, windows-latest, macos-latest]
+        os: [ubuntu-latest, windows-latest, macos-latest]
     steps:
       - uses: actions/checkout@v2
       # test old versions which didn't have npm and layout different