Replace {@removed} with @removed

In most places the `@removed` doctag is treated as a block tag on its
own line. However, there are a few places where it is treated as an
inline doctag, i.e. `{@removed}`. Dealing with both types increases the
complexity of Metalava and makes it slightly slower.

This change replaces the inline doctag form `{@removed}` with a block
tag.

Flag: EXEMPT replacing {@removed} with @removed does not change API or behavior
Bug: 429965593
Test: m checkapi
Change-Id: I62c9d2710265eec1c55ba964991eeeb15816e870