Fixes NL postcode (#1197)

* An effort was made in 12df44f
to account for Netherlands postcodes never including the letters SS, SD,
or SA. This let to some odd output, as mentioned in #1188.

* The issue, as far as I can tell, is that `Faker#regexify` is built to
handle negative lookbehind regexes.

* This is a naive solution, but simple hardcodes all the allowed letter
combos in.

* As for a test case, the previously implemented one as `test_nl_postcode`
was actually an intermittent failure (which could be seen by running it
a bunch of times in a row). I've kept it as is because I'm not sure how
to make it better, short of telling it to execute a ton of times (which
seems silly). Open to ideas on that.

lib/locales/nl.yml

@@ -44,7 +44,7 @@ nl:
 
       street_address:
         - "#{street_name} #{building_number}"
-      postcode: /\d{4} [A-Z]{2}(?<!SA|SS|SD)/
+      postcode: /\d{4} (AA|AB|AC|AD|AE|AF|AG|AH|AI|AJ|AK|AL|AM|AN|AO|AP|AQ|AR|AS|AT|AU|AV|AW|AX|AY|AZ|BA|BB|BC|BD|BE|BF|BG|BH|BI|BJ|BK|BL|BM|BN|BO|BP|BQ|BR|BS|BT|BU|BV|BW|BX|BY|BZ|CA|CB|CC|CD|CE|CF|CG|CH|CI|CJ|CK|CL|CM|CN|CO|CP|CQ|CR|CS|CT|CU|CV|CW|CX|CY|CZ|DA|DB|DC|DD|DE|DF|DG|DH|DI|DJ|DK|DL|DM|DN|DO|DP|DQ|DR|DS|DT|DU|DV|DW|DX|DY|DZ|EA|EB|EC|ED|EE|EF|EG|EH|EI|EJ|EK|EL|EM|EN|EO|EP|EQ|ER|ES|ET|EU|EV|EW|EX|EY|EZ|FA|FB|FC|FD|FE|FF|FG|FH|FI|FJ|FK|FL|FM|FN|FO|FP|FQ|FR|FS|FT|FU|FV|FW|FX|FY|FZ|GA|GB|GC|GD|GE|GF|GG|GH|GI|GJ|GK|GL|GM|GN|GO|GP|GQ|GR|GS|GT|GU|GV|GW|GX|GY|GZ|HA|HB|HC|HD|HE|HF|HG|HH|HI|HJ|HK|HL|HM|HN|HO|HP|HQ|HR|HS|HT|HU|HV|HW|HX|HY|HZ|IA|IB|IC|ID|IE|IF|IG|IH|II|IJ|IK|IL|IM|IN|IO|IP|IQ|IR|IS|IT|IU|IV|IW|IX|IY|IZ|JA|JB|JC|JD|JE|JF|JG|JH|JI|JJ|JK|JL|JM|JN|JO|JP|JQ|JR|JS|JT|JU|JV|JW|JX|JY|JZ|KA|KB|KC|KD|KE|KF|KG|KH|KI|KJ|KK|KL|KM|KN|KO|KP|KQ|KR|KS|KT|KU|KV|KW|KX|KY|KZ|LA|LB|LC|LD|LE|LF|LG|LH|LI|LJ|LK|LL|LM|LN|LO|LP|LQ|LR|LS|LT|LU|LV|LW|LX|LY|LZ|MA|MB|MC|MD|ME|MF|MG|MH|MI|MJ|MK|ML|MM|MN|MO|MP|MQ|MR|MS|MT|MU|MV|MW|MX|MY|MZ|NA|NB|NC|ND|NE|NF|NG|NH|NI|NJ|NK|NL|NM|NN|NO|NP|NQ|NR|NS|NT|NU|NV|NW|NX|NY|NZ|OA|OB|OC|OD|OE|OF|OG|OH|OI|OJ|OK|OL|OM|ON|OO|OP|OQ|OR|OS|OT|OU|OV|OW|OX|OY|OZ|PA|PB|PC|PD|PE|PF|PG|PH|PI|PJ|PK|PL|PM|PN|PO|PP|PQ|PR|PS|PT|PU|PV|PW|PX|PY|PZ|QA|QB|QC|QD|QE|QF|QG|QH|QI|QJ|QK|QL|QM|QN|QO|QP|QQ|QR|QS|QT|QU|QV|QW|QX|QY|QZ|RA|RB|RC|RD|RE|RF|RG|RH|RI|RJ|RK|RL|RM|RN|RO|RP|RQ|RR|RS|RT|RU|RV|RW|RX|RY|RZ|SB|SC|SE|SF|SG|SH|SI|SJ|SK|SL|SM|SN|SO|SP|SQ|SR|ST|SU|SV|SW|SX|SY|SZ|TA|TB|TC|TD|TE|TF|TG|TH|TI|TJ|TK|TL|TM|TN|TO|TP|TQ|TR|TS|TT|TU|TV|TW|TX|TY|TZ|UA|UB|UC|UD|UE|UF|UG|UH|UI|UJ|UK|UL|UM|UN|UO|UP|UQ|UR|US|UT|UU|UV|UW|UX|UY|UZ|VA|VB|VC|VD|VE|VF|VG|VH|VI|VJ|VK|VL|VM|VN|VO|VP|VQ|VR|VS|VT|VU|VV|VW|VX|VY|VZ|WA|WB|WC|WD|WE|WF|WG|WH|WI|WJ|WK|WL|WM|WN|WO|WP|WQ|WR|WS|WT|WU|WV|WW|WX|WY|WZ|XA|XB|XC|XD|XE|XF|XG|XH|XI|XJ|XK|XL|XM|XN|XO|XP|XQ|XR|XS|XT|XU|XV|XW|XX|XY|XZ|YA|YB|YC|YD|YE|YF|YG|YH|YI|YJ|YK|YL|YM|YN|YO|YP|YQ|YR|YS|YT|YU|YV|YW|YX|YY|YZ|ZA|ZB|ZC|ZD|ZE|ZF|ZG|ZH|ZI|ZJ|ZK|ZL|ZM|ZN|ZO|ZP|ZQ|ZR|ZS|ZT|ZU|ZV|ZW|ZX|ZY|ZZ)/
       state: ["Noord-Holland", "Zuid-Holland", "Utrecht", "Zeeland", "Overijssel", "Gelderland", "Drenthe", "Friesland", "Groningen", "Noord-Brabant", "Limburg"]
       default_country: [Nederland]