Remove DISABLE_STRING variables after PR#16848 (#17367)

Signed-off-by: Takuya Noguchi <takninnovationresearch@gmail.com>

.gitpod.yml

@@ -13,8 +13,6 @@ ports:
 
 tasks:
   - name: Forem Server
-    env:
-      DISABLE_SPRING: 1
     before: >
       redis-server &
       gp await-port 5432 &&

.travis.yml

@@ -41,7 +41,6 @@ env:
     - KNAPSACK_PRO_CI_NODE_TOTAL=3
     - COVERAGE_REPORTS_TOTAL=4
     - FOREM_OWNER_SECRET="secret" # test secret so e2e tests can run properly.
-    - DISABLE_SPRING=true
 before_install:
   - sudo apt-get update
   - sudo apt-get -y install gsfonts