lib/shopt: remove nocasematch

The setting `shopt -s nocasematch` affects every pattern matching in
Bash including the case statement, [[ str == pat ]] matching,
${var/pat/rep}, and ${var#pat}.  Since the affected range is too
large, this potentially breaks the exiting functions.  I think this
settings `shopt -s nocasematch` should be enabled locally when it is
specifically needed rather than enabling it globally.

lib/shopt.sh

@@ -25,10 +25,8 @@ shopt -s globstar 2> /dev/null
 # (used in case, [[]], word expansions and command completions)
 if [[ ${OMB_CASE_SENSITIVE:-${CASE_SENSITIVE:-}} == true ]]; then
    shopt -u nocaseglob
-   shopt -u nocasematch
 else
    shopt -s nocaseglob
-   shopt -s nocasematch
 fi
 
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