goprotobuf: Remove all but go.r60 from .hgtags.

R=bradfitz, r, r, rsc
CC=golang-dev
http://codereview.appspot.com/5946044

.hgtags

@@ -1,24 +1 @@
-96dad172ec5b1aa6946f13f9cbf9cfe0fec40f05 weekly.2011-04-04
-37b09d1346b72c73a76672aa9a830bff9e6be014 weekly.2011-04-13
-44f4e3da3f952834d65c7a5fcc1f1a2cc90e1542 weekly.2011-04-27
-097a1c90eb4bf73ecacbcef71c09298f4a596dcd weekly.2011-06-16
-83a0b16ac3234242663b12be19adc030c1cd666a weekly.2011-06-23
-89e4e9b619197f71e60c3ed309474cfd94475061 weekly.2011-07-07
-32017900448961add50b154f63d1f80907285984 weekly.2011-08-10
-c9278633d1eb1c80bc5946eb6724e2d22cd28265 weekly.2011-08-17
-f3ef978cda6fabc10f6039aeed960340547c6d5a release.r56
-fa1080cfc0a4d0fa24844bc50124aed892365059 release.r57.1
-fa1080cfc0a4d0fa24844bc50124aed892365059 release.r57.2
-cfe37a63cede6cd072434965e6ea426b90bcb223 release.r58
-cfe37a63cede6cd072434965e6ea426b90bcb223 release.r58.1
-da17c98c73d8801baa1d2e493c9ac0844470ef0a release.r59
 f0f9983b6de6764a416f90d31440f01b54233228 go.r60
-5a487ccac6f7fd6cba5deee5d5d0908c7f1d6a53 go.weekly.2011-09-07
-bc76a153ffde5de8535b7c2791102ddd0b93f187 go.weekly.2011-09-21
-a13c0e6343c49dc738c218ea43cab675865136dc go.weekly.2011-10-26
-694312d6c9bb86513f52e38db02c2d0f84b181ce go.weekly.2011-11-02
-458bd32e66bc173c6c12743d375dfa20b145a31f go.weekly.2011-11-09
-baa3174c862d6d0b5a44044c385736f633e10a85 go.weekly.2011-12-06
-be6d136a075ad78f0ec0348dd6056f57dc08b8b7 go.weekly.2012-02-07
-b33dd4d56caa97d629c954cf149d67eb595cc49e go.weekly.2012-02-22
-b33dd4d56caa97d629c954cf149d67eb595cc49e weekly