fix backend string

Author: nmwsharp

.github/workflows/linux.yml

@@ -31,7 +31,7 @@ jobs:
       run: cd test/build && ./bin/polyscope-test --gtest_catch_exceptions=0 backend=openGL_mock
 
     - name: run test egl backend
-      run: cd test/build && ./bin/polyscope-test --gtest_catch_exceptions=0 backend=openGL_egl
+      run: cd test/build && ./bin/polyscope-test --gtest_catch_exceptions=0 backend=openGL3_egl
 
   build_shared:
     strategy:
@@ -57,4 +57,4 @@ jobs:
       run: cd test/build && ./bin/polyscope-test --gtest_catch_exceptions=0 backend=openGL_mock
 
     - name: run test egl backend
-      run: cd test/build && ./bin/polyscope-test --gtest_catch_exceptions=0 backend=openGL_egl
+      run: cd test/build && ./bin/polyscope-test --gtest_catch_exceptions=0 backend=openGL3_egl