[RISC-V] Increase timeouts in CacheTests (#107278)

This patch fixes System.Text.Json.Serialization.Tests.CacheTests on Debug build.

Author: yurai007

src/libraries/System.Text.Json/tests/System.Text.Json.Tests/Serialization/CacheTests.cs

@@ -239,6 +239,8 @@ public static void JsonSerializerOptionsUpdateHandler_ClearingDoesntPreventSeria
 
                     JsonSerializer.Serialize<SimpleTestClass>(testObj, options);
                     Assert.NotEqual(0, getCount(options));
+                }, new RemoteInvokeOptions() {
+                    TimeOut = RemoteExecutor.FailWaitTimeoutMilliseconds * PlatformDetection.SlowRuntimeTimeoutModifier
                 }).Dispose();
 
             static Func<JsonSerializerOptions, int> CreateCacheCountAccessor()
@@ -294,6 +296,8 @@ public static void JsonSerializerOptions_ReuseConverterCaches()
                         Assert.Same(originalCacheOptions, getCacheOptions(options2));
                     }
                 }
+            }, new RemoteInvokeOptions() {
+                TimeOut = RemoteExecutor.FailWaitTimeoutMilliseconds * PlatformDetection.SlowRuntimeTimeoutModifier
             }).Dispose();
 
             static Func<JsonSerializerOptions, JsonSerializerOptions?> CreateCacheOptionsAccessor()