errata: Bashの正称を修正

[uenojp]

Bashの正称はBourne Shellではなく、Bourne Again Shellです。

Bash is the GNU Project's shell—the Bourne Again SHell.

ref. https://www.gnu.org/software/bash/

BashとBourne Shellは別のシェルであり、BashはBourne Shellの後継シェルのうちの一つです。

Bash contains features that appear in other popular shells, and some features that only appear in Bash. Some of the shells that Bash has borrowed concepts from are the Bourne Shell (sh), the Korn Shell (ksh), and the C-shell (csh and its successor, tcsh).

ref. https://www.gnu.org/software/bash/manual/bash.html