Request to change ruby default version to 2.5

[Walter Schwarzenfeld]

Thanks! Builds fine without DOCS=on.

With DOCS=on

/usr/bin/strip 
/ram/usr/ports/databases/ruby-bdb/work/stage/usr/local/lib/ruby/site_ruby/2.5/amd64-freebsd11/bdb.so
/bin/mkdir -p 
/ram/usr/ports/databases/ruby-bdb/work/stage/usr/local/share/doc/ruby25/bdb/doc
(cd /ram/usr/ports/databases/ruby-bdb/work/bdb-0.6.6 && install  -m 0644 
Changes README.en bdb.rd docs/*.rd 
/ram/usr/ports/databases/ruby-bdb/work/stage/usr/local/share/doc/ruby25/bdb)
(cd /ram/usr/ports/databases/ruby-bdb/work/bdb-0.6.6/docs/doc && /bin/sh 
-c '(/usr/bin/find -Ed $1 $3 | /usr/bin/cpio -dumpl $2 >/dev/null 2>&1) 
&&  /usr/bin/find -Ed $1 $3 \(   -type d -exec /bin/sh -c '\''cd 
'\''$2'\'' && chmod 755 "$@"'\'' . {} +  -o -type f -exec /bin/sh -c 
'\''cd '\''$2'\'' && chmod 0644 "$@"'\'' . {} + \)' COPYTREE_SHARE . 
/ram/usr/ports/databases/ruby-bdb/work/stage/usr/local/share/doc/ruby25/bdb/doc)
cd: /ram/usr/ports/databases/ruby-bdb/work/bdb-0.6.6/docs/doc: No such 
file or directory
*** Error code 2

Stop.
make[1]: stopped in /usr/ports/databases/ruby-bdb
*** Error code 1