CI: Do not run benchmarks on Py2.7.

Author: scoder

.github/workflows/ci.yml

@@ -77,6 +77,7 @@ jobs:
       run: make testslow
 
     - name: Running benchmark
+      if: startsWith(matrix.python-version, '3.')
       run: |
         python benchmark/telco_fractions.py -n 250
         python benchmark/microbench.py create pydigits
@@ -200,6 +201,7 @@ jobs:
         if-no-files-found: ignore
 
     - name: Running benchmark
+      if: startsWith(matrix.python-version, '3.')
       run: |
         python benchmark/telco_fractions.py -n 250
         python benchmark/microbench.py create pydigits