new way of setting env variables in GH Actions (#4700)

Co-authored-by: Dirk Groeneveld <dirkg@allenai.org>

.github/workflows/master.yml

@@ -21,9 +21,9 @@ jobs:
     - name: Set Docker tag
       run: |
         if [[ $GITHUB_EVENT_NAME == 'release' ]]; then
-            echo "::set-env name=DOCKER_TAG::${GITHUB_REF#refs/tags/}";
+            echo "DOCKER_TAG=${GITHUB_REF#refs/tags/}" >> $GITHUB_ENV;
         else
-            echo "::set-env name=DOCKER_TAG::$GITHUB_SHA";
+            echo "DOCKER_TAG=$GITHUB_SHA" >> $GITHUB_ENV;
         fi
 
     - name: Build test image
@@ -186,7 +186,7 @@ jobs:
         # This is somewhat bizarre, but you can't set env variables to bash
         # commands in the action workflow - so we have to use this odd way of
         # exporting a variable instead.
-        echo ::set-env name=ALLENNLP_VERSION_SUFFIX::.dev$(date -u +%Y%m%d)
+        echo "ALLENNLP_VERSION_SUFFIX=dev$(date -u +%Y%m%d)" >> $GITHUB_ENV
 
     - name: Check version and release tag match
       if: github.event_name == 'release'
@@ -270,9 +270,9 @@ jobs:
     - name: Set Docker image name
       run: |
         if [[ $GITHUB_EVENT_NAME == 'release' ]]; then
-            echo "::set-env name=DOCKER_IMAGE_NAME::allennlp/allennlp:${GITHUB_REF#refs/tags/}";
+            echo "DOCKER_IMAGE_NAME=allennlp/allennlp:${GITHUB_REF#refs/tags/}" >> $GITHUB_ENV;
         else
-            echo "::set-env name=DOCKER_IMAGE_NAME::allennlp/commit:$GITHUB_SHA";
+            echo "DOCKER_IMAGE_NAME=allennlp/commit:$GITHUB_SHA" >> $GITHUB_ENV;
         fi
 
     - name: Download core package
@@ -360,9 +360,9 @@ jobs:
     - name: Set target folders
       run: |
         if [[ $GITHUB_EVENT_NAME == 'release' ]]; then
-            echo "::set-env name=DOCS_FOLDER::${GITHUB_REF#refs/tags/}";
+            echo "DOCS_FOLDER=${GITHUB_REF#refs/tags/}" >> $GITHUB_ENV;
         else
-            echo "::set-env name=DOCS_FOLDER::master";
+            echo "DOCS_FOLDER=master" >> $GITHUB_ENV;
         fi
 
     - name: Stage docs

.github/workflows/pull_request.yml

@@ -33,7 +33,7 @@ jobs:
 
     - name: Set Docker tag
       run: |
-        echo "::set-env name=DOCKER_TAG::$GITHUB_SHA";
+        echo "DOCKER_TAG=$GITHUB_SHA" >> $GITHUB_ENV
 
     - name: Build test image
       run: |