Fix form item height problem

close #8701

revert fix of #6097 cause it does not exist in 3.x

components/form/style/index.less

@@ -243,22 +243,6 @@ form {
   .@{ant-prefix}-select,
   .@{ant-prefix}-cascader-picker {
     width: 100%;
-    // Fix https://github.com/ant-design/ant-design/issues/6097
-    &:only-child {
-      display: block;
-      position: relative;
-      top: (@form-component-max-height - @input-height-base) / 2;
-
-      &.@{ant-prefix}-select-sm,
-      &.@{ant-prefix}-cascader-picker-small {
-        top: (@form-component-max-height - @input-height-sm) / 2;
-      }
-
-      &.@{ant-prefix}-select-lg,
-      &.@{ant-prefix}-cascader-picker-large {
-        top: (@form-component-max-height - @input-height-lg) / 2;
-      }
-    }
   }
 
   // Don't impact select inside input group
@@ -267,25 +251,6 @@ form {
     width: auto;
   }
 
-  // Don't impact select inside input group addon
-  .@{ant-prefix}-input-group-addon .@{ant-prefix}-select,
-  .@{ant-prefix}-input-group-addon .@{ant-prefix}-cascader-picker {
-    &:only-child {
-      display: inline-block;
-      top: 0;
-
-      &.@{ant-prefix}-select-sm,
-      &.@{ant-prefix}-cascader-picker-small {
-        top: 0;
-      }
-
-      &.@{ant-prefix}-select-lg,
-      &.@{ant-prefix}-cascader-picker-large {
-        top: 0;
-      }
-    }
-  }
-
   // fix input with addon position. https://github.com/ant-design/ant-design/issues/8243
   .@{ant-prefix}-input-group-wrapper {
     position: relative;