bsdgrep: disable TRE implementation by default

Start the phasing out of TRE by disabling it by default. r317254 introduced
a BSD_GREP_FASTMATCH knob (defaulting to on) for testing of bsdgrep with and
without TRE enabled. More bugs have cropped up since then, and
WITHOUT_BSD_GREP_FASTMATCH has shown in testing to be more stable than its
counterpart.

Approved by:	emaste (mentor)
Differential Revision:	https://reviews.freebsd.org/D12381

share/mk/src.opts.mk

@@ -62,7 +62,6 @@ __DEFAULT_YES_OPTIONS = \
     BOOTPARAMD \
     BOOTPD \
     BSD_CPIO \
-    BSD_GREP_FASTMATCH \
     BSDINSTALL \
     BSNMP \
     BZIP2 \
@@ -175,6 +174,7 @@ __DEFAULT_YES_OPTIONS = \
 
 __DEFAULT_NO_OPTIONS = \
     BSD_GREP \
+    BSD_GREP_FASTMATCH \
     CLANG_EXTRAS \
     DTRACE_TESTS \
     GNU_GREP_COMPAT \