RFR: 8278548: G1: Remove unnecessary check in forward_to_block_containing_addr [v2]

[Albert Mingkun Yang]

> Simple change of removing an always-false `if`.
> 
> Test: I added `assert(false)` inside the `if`, and no failure in tier1-6.

Albert Mingkun Yang has updated the pull request incrementally with one additional commit since the last revision:

  review

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/6797/files
  - new: https://git.openjdk.java.net/jdk/pull/6797/files/326ce362..52e49e17

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=6797&range=01
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=6797&range=00-01

  Stats: 1 line in 1 file changed: 1 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/6797.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/6797/head:pull/6797

PR: https://git.openjdk.java.net/jdk/pull/6797