tests/examples: Drop support for PNG output images

No currently existing test produces a PNG image, so why do we even check
for such an output file?

I did 'rm -rf build && make -j9 && cp -r build /tmp', then applied this
patch, and then did another 'rm -rf build && make -j9'. According to
diff, the resulting directories are basically the same (except for lots
of timestamps and some non-determinism in CMake).

Signed-off-by: Uli Schlachter <psychon@znc.in>

tests/examples/CMakeLists.txt

@@ -186,9 +186,7 @@ function(run_test test_path namespace escaped_content)
     get_filename_component(${test_path} TEST_FILE_NAME NAME)
     set(IMAGE_PATH "${IMAGE_DIR}/AUTOGEN${namespace}_${TEST_FILE_NAME}")
 
-    # Execute the script, leave the image extension decision to the test.
-    # SVG is preferred, but PNG is better suited for some tests, like bitmap
-    # patterns.
+    # Execute the script.
     file(RELATIVE_PATH rel_test_path "${TOP_SOURCE_DIR}" "${test_path}")
     message(STATUS "Running ${rel_test_path}…")
 
@@ -224,12 +222,6 @@ function(run_test test_path namespace escaped_content)
             "![Usage example](../images/AUTOGEN${namespace}_${TEST_FILE_NAME}.svg)\n"
             "${TEST_DOC_CONTENT}" TEST_DOC_CONTENT ""
         )
-    elseif(EXISTS "${IMAGE_PATH}.png")
-        set(OUTPUT_IMAGE_PATH "${IMAGE_PATH}.png")
-        escape_string(
-            "![Usage example](../images/AUTOGEN${namespace}_${TEST_FILE_NAME}.png)\n"
-            "${TEST_DOC_CONTENT}" TEST_DOC_CONTENT ""
-        )
     else()
         set(OUTPUT_IMAGE_PATH "")
     endif()