simplify .gitattributes

This was brought up in #1607 and I think it's preferable.

Author: Byron

.gitattributes

@@ -1,11 +1,11 @@
-**/generated-archives/*.tar* filter=lfs-disabled diff=lfs merge=lfs -text
+generated-archives/*.tar* filter=lfs-disabled diff=lfs merge=lfs -text
 
 # assure line feeds don't interfere with our working copy hash
-**/tests/fixtures/**/*.sh text crlf=input	eol=lf
+tests/fixtures/**/*.sh text crlf=input	eol=lf
 /justfile text crlf=input	eol=lf
 
 # have GitHub include fixture-making scripts when it counts code
-**/tests/fixtures/**/*.sh linguist-vendored=false
+tests/fixtures/**/*.sh linguist-vendored=false
 
 # have GitHub treat the gix-packetline-blocking src copy as auto-generated
 gix-packetline-blocking/src/ linguist-generated=true