fix: solve the problem of the tag input becoming a title after the # symbol

[LIlGG]

What type of PR is this?

/kind bug

What this PR does / why we need it:

由于 ExtensionHeading 的输入规则与 moment 的 ExtensionTag 规则相冲突，导致输入 # 号之后按回车会变为标题。

也尝试过将 Priority 设置为较大的数值。但并没有效果，因为 ExtensionTag 是 Mark 而 ExtensionHeading 是一个 Node，因此他们之间的输入规则会同时触发。

综上所述，目前采取的策略是移除 ExtensionHeading 扩展。

此改动需要 Halo 2.12.0 的支持。

How to test it?

在 moment 页面中输入 # 后按回车，查看是否变为标签而不是其他内容。

Which issue(s) this PR fixes:

Fixes #65

Does this PR introduce a user-facing change?

解决在编辑区域输入 # 号后变为标题而不是标签的问题

[guqing]

/lgtm

[guqing]

有冲突需要解决

[f2c-ci-robot]

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[guqing]

/lgtm