Clean up temporary BoringSSL #ifdefs. (#232)

I believe these are no longer necessary.
diff --git a/common/src/jni/main/cpp/NativeCrypto.cpp b/common/src/jni/main/cpp/NativeCrypto.cpp
index f2852ac..0d249f8 100644
--- a/common/src/jni/main/cpp/NativeCrypto.cpp
+++ b/common/src/jni/main/cpp/NativeCrypto.cpp
@@ -568,22 +568,6 @@
   return ex_data->cached_size;
 }
 
-// TODO(davidben): Remove this once
-// https://boringssl-review.googlesource.com/c/15864/ is in all Conscrypt
-// consumers.
-#if BORINGSSL_API_VERSION < 4
-int RsaMethodEncrypt(RSA* /* rsa */,
-                     size_t* /* out_len */,
-                     uint8_t* /* out */,
-                     size_t /* max_out */,
-                     const uint8_t* /* in */,
-                     size_t /* in_len */,
-                     int /* padding */) {
-  OPENSSL_PUT_ERROR(RSA, RSA_R_UNKNOWN_ALGORITHM_TYPE);
-  return 0;
-}
-#endif
-
 int RsaMethodSignRaw(RSA* rsa,
                      size_t* out_len,
                      uint8_t* out,
@@ -755,12 +739,6 @@
 
     g_rsa_method.common.is_static = 1;
     g_rsa_method.size = RsaMethodSize;
-    // TODO(davidben): Remove this once
-    // https://boringssl-review.googlesource.com/c/15864/ is in all Conscrypt
-    // consumers.
-#if BORINGSSL_API_VERSION < 4
-    g_rsa_method.encrypt = RsaMethodEncrypt;
-#endif
     g_rsa_method.sign_raw = RsaMethodSignRaw;
     g_rsa_method.decrypt = RsaMethodDecrypt;
     g_rsa_method.flags = RSA_FLAG_OPAQUE;