ci(travis): update php versions

Author: domtra

.travis.yml

@@ -18,21 +18,19 @@ env:
   - COMPOSER_FLAGS="--prefer-stable --prefer-source"
 
 php:
-  - 5.6
-  - 7.0
-  - 7.1
-  - 7.2
-  - 7.3
   - 7.4
+  - 8.0
+  - 8.1
+  - 8.2
   - nightly
 
 matrix:
   fast_finish: true
   include:
-    - php: 7.1
+    - php: 8.1
       env:
         - COMPOSER_FLAGS="--prefer-lowest --prefer-stable --prefer-source"
-    - php: 7.1
+    - php: 8.1
       env:
         - TEST_VERSION=true
         - COMPOSER_FLAGS="--prefer-stable --prefer-source"