fix: close lsif file after writing

[crackcomm]

The dump.lsif contained malformed JSON output, for example:

{"id":139,"type":"vertex","label":"range","start":{"line":4,"character":11},"end":{"line":4,"character":18}}
{"id":140,"type":"edge","label":"next","inV":39,"outV":139}
{"id":141,"type":"edge","label":"item","inVs":[139],"outV":40,"document":124,"property":"references"}
{"id":142,"type":"edge","label":"contains","inVs":[125,129,132,135,139],"outV":124}
"line":4,"character":18}}
{"id":143,"type":"edge","label":"next","inV":39,"outV":142}

This in turn caused warnings and sometimes crashes:

WARN[0000] invalid json format: V":124}

WARN[0000] invalid json format: "line":4,"character":18}}
panic: EOF

goroutine 1 [running]:
main.panicIfErr(...)
        /home/pah/ocxmr-repos/opt/srctx/cmd/srctx/main.go:31
main.mainFunc({0xc0000360a0, 0xa, 0xa})
        /home/pah/ocxmr-repos/opt/srctx/cmd/srctx/main.go:26 +0x145
main.main()
        /home/pah/ocxmr-repos/opt/srctx/cmd/srctx/main.go:13 +0x2e

This hopefully fixes the bug, it does in my limited testing.

[codecov]

Codecov Report

Attention: 8 lines in your changes are missing coverage. Please review.

Comparison is base (6e0c5dc) 62.22% compared to head (7f8d606) 64.78%.

Files	Patch %	Lines
parser/api.go	0.00%	8 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #70      +/-   ##
==========================================
+ Coverage   62.22%   64.78%   +2.56%     
==========================================
  Files          48       48              
  Lines        3044     3050       +6     
==========================================
+ Hits         1894     1976      +82     
+ Misses        910      836      -74     
+ Partials      240      238       -2     

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