Minor GPML Match clause clean-up

[jpschorr]

Part of the exploration of #689

Minor clean-up after #652 and #658 :

• Clean up some linter warnings
• Require parentheses around implicitly joined (via comma) graph patterns in the MATCH clause.

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[codecov-commenter]

Codecov Report

Merging #663 (da319dc) into main (bf2696f) will increase coverage by 0.00%.
The diff coverage is 50.00%.

@@            Coverage Diff            @@
##               main     #663   +/-   ##
=========================================
  Coverage     79.61%   79.61%           
  Complexity     2349     2349           
=========================================
  Files           236      236           
  Lines         19345    19336    -9     
  Branches       3765     3764    -1     
=========================================
- Hits          15401    15394    -7     
+ Misses         2657     2656    -1     
+ Partials       1287     1286    -1     

Flag	Coverage Δ
CLI	22.68% <ø> (ø)
EXAMPLES	76.24% <ø> (ø)
EXTENSIONS	69.23% <ø> (ø)
LANG	81.67% <50.00%> (+<0.01%)	⬆️
PTS	∅ <ø> (∅)
TEST_SCRIPT	77.98% <ø> (ø)

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Impacted Files	Coverage Δ
lang/src/org/partiql/lang/syntax/SqlParser.kt	77.75% <50.00%> (-0.01%)	⬇️

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