challenge: use portable [{] literal-brace in _egrep_o patterns (#968)

_egrep_o falls back to a BRE sed expression on shells without egrep -o
(Solaris, DD-WRT busybox). A bare "\{" there is a BRE interval operator
and aborts ("sed: command garbled" / "Invalid content of \{\}"), so the
challenge-status-invalid path extracted an empty error object and the
CA's failure reason was lost. Replace the escaped braces with "[{]"/"[}]"
bracket expressions, unambiguous literal braces in both BRE and ERE, at
all four call sites (challenge type/error extraction and profiles).

acme.sh

@@ -5304,7 +5304,7 @@ $_authorizations_map"
       fi
 
       # Fix for empty error objects in response which mess up the original code, adapted from fix suggested here: https://github.com/acmesh-official/acme.sh/issues/4933#issuecomment-1870499018
-      entry="$(echo "$response" | sed s/'"error":{}'/'"error":null'/ | _egrep_o '[^\{]*"type":"'$vtype'"[^\}]*')"
+      entry="$(echo "$response" | sed s/'"error":{}'/'"error":null'/ | _egrep_o '[^{]*"type":"'$vtype'"[^}]*')"
       _debug entry "$entry"
 
       if [ -z "$keyauthorization" -a -z "$entry" ]; then
@@ -5636,7 +5636,7 @@ $_authorizations_map"
       status=$(echo "$response" | _egrep_o '"status":"[^"]*' | cut -d : -f 2 | tr -d '"')
       _debug2 status "$status"
       if _contains "$status" "invalid"; then
-        error="$(echo "$response" | _egrep_o '"error":\{[^\}]*')"
+        error="$(echo "$response" | _egrep_o '"error":[{][^}]*')"
         _debug2 error "$error"
         errordetail="$(echo "$error" | _egrep_o '"detail": *"[^"]*' | cut -d '"' -f 4)"
         _debug2 errordetail "$errordetail"
@@ -6581,7 +6581,7 @@ list_profiles() {
   fi
 
   normalized_response=$(echo "$response" | _normalizeJson)
-  profiles_json=$(echo "$normalized_response" | _egrep_o '"profiles" *: *\{[^\}]*\}')
+  profiles_json=$(echo "$normalized_response" | _egrep_o '"profiles" *: *[{][^}]*[}]')
 
   if [ -z "$profiles_json" ]; then
     _info "The CA '$_l_server_name' does not publish certificate profiles via its directory endpoint."
@@ -7264,7 +7264,7 @@ _deactivate() {
     _debug "Trigger validation."
     vtype="$(_getIdType "$_d_domain")"
     # Fix for empty error objects in response which mess up the original code, adapted from fix suggested here: https://github.com/acmesh-official/acme.sh/issues/4933#issuecomment-1870499018
-    entry="$(echo "$response" | sed s/'"error":{}'/'"error":null'/ | _egrep_o '[^\{]*"type":"'$vtype'"[^\}]*')"
+    entry="$(echo "$response" | sed s/'"error":{}'/'"error":null'/ | _egrep_o '[^{]*"type":"'$vtype'"[^}]*')"
     _debug entry "$entry"
     if [ -z "$entry" ]; then
       _err "$d: Cannot get domain token"