Update .travis.yml

.travis.yml

@@ -293,8 +293,8 @@ matrix:
       addons:
         apt:
           packages:
-            - gcc-11
-            - gfortran-11
+            - gcc-10
+            - gfortran-10
             - wget
       script:
         - wget https://developer.arm.com/-/media/Files/downloads/hpc/arm-instruction-emulator/21-0/ARM-Instruction-Emulator_21.0_AArch64_Ubuntu-18.04_aarch64.tar.gz?revision=f2d90a6c-15c5-42b3-81aa-464f30efc954