build: 规范建表语句的字符集

backend/src/main/resources/db/migration/V97__v1.14_release.sql

@@ -390,7 +390,7 @@ CREATE TABLE `test_plan_follow`
     `follow_id`    varchar(50) DEFAULT NULL COMMENT '关注人',
     UNIQUE KEY `test_plan_principal_pk` (`test_plan_id`, `follow_id`)
 ) ENGINE = InnoDB
-  DEFAULT CHARSET = utf8mb4;
+  DEFAULT CHARSET = utf8mb4 COLLATE utf8mb4_general_ci;
 
 INSERT INTO test_plan_follow
 SELECT id, follow_people

backend/src/main/resources/db/migration/V99__v1.15_release.sql

@@ -6,7 +6,7 @@ CREATE TABLE `issue_follow`
     KEY `issue_follow_follow_id_index` (`follow_id`),
     KEY `issue_follow_issue_id_index` (`issue_id`)
 ) ENGINE = InnoDB
-  DEFAULT CHARSET = utf8mb4;
+  DEFAULT CHARSET = utf8mb4 COLLATE utf8mb4_general_ci;
 
 -- group
 INSERT INTO user_group_permission (id, group_id, permission_id, module_id)