Fix RST syntax in README

Author: MatthiasValvekens

README.rst

@@ -21,7 +21,7 @@ features.
 Historically, this project used to run continuous integration tests against several
 HSM platforms, but this test setup has not been maintained over time. Currently,
 the integration tests in GitHub Actions use SoftHSMv2 as a baseline.
-We also test against `opencryptoki` in CI. If you would like
+We also test against ``opencryptoki`` in CI. If you would like
 to contribute some CI setup with additional PKCS#11 implementations or actual HSMs,
 let's chat!